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Ophry Pines - One of the best experts on this subject based on the ideXlab platform.
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yeast Aconitase mitochondrial import is modulated by interactions of its c and n terminal domains and ssa1 2 hsp70
Scientific Reports, 2018Co-Authors: Reut Benmenachem, Katherine Wang, Orly Marcu, Teck Kwang Lim, Qingsong Lin, Ora Schuelerfurman, Ophry PinesAbstract:Molecules of single proteins, echoforms, can be distributed between two (or more) subcellular locations, a phenomenon which we refer to as dual targeting or dual localization. The yeast Aconitase gene ACO1 (778 amino acids), encodes a single translation product that is nonetheless dual localized to the cytosol and mitochondria by a reverse translocation mechanism. The solved crystal structure of Aconitase isolated from porcine heart mitochondria shows that it has four domains. The first three tightly associated N-terminal domains are tethered to the larger C-terminal fourth domain (C-terminal amino acids 517-778). We have previously shown that the Aconitase C terminal domain constitutes an independent dual targeting signal when fused to mitochondria-targeted passenger-proteins. We show that the Aconitase N and C-terminal domains interact and that this interaction is important for efficient Aconitase post translational import into mitochondria and for Aconitase dual targeting (relative levels of Aconitase echoforms). Our results suggest a "chaperone-like function" of the C terminal domain towards the N terminal domains which can be modulated by Ssa1/2 (cytosolic Hsp70).
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Yeast Aconitase mitochondrial import is modulated by interactions of its C and N terminal domains and Ssa1/2 (Hsp70)
Nature Publishing Group, 2018Co-Authors: Reut Ben-menachem, Katherine Wang, Orly Marcu, Teck Kwang Lim, Qingsong Lin, Ora Schueler- Furman, Ophry PinesAbstract:Abstract Molecules of single proteins, echoforms, can be distributed between two (or more) subcellular locations, a phenomenon which we refer to as dual targeting or dual localization. The yeast Aconitase gene ACO1 (778 amino acids), encodes a single translation product that is nonetheless dual localized to the cytosol and mitochondria by a reverse translocation mechanism. The solved crystal structure of Aconitase isolated from porcine heart mitochondria shows that it has four domains. The first three tightly associated N-terminal domains are tethered to the larger C-terminal fourth domain (C-terminal amino acids 517–778). We have previously shown that the Aconitase C terminal domain constitutes an independent dual targeting signal when fused to mitochondria-targeted passenger-proteins. We show that the Aconitase N and C-terminal domains interact and that this interaction is important for efficient Aconitase post translational import into mitochondria and for Aconitase dual targeting (relative levels of Aconitase echoforms). Our results suggest a “chaperone-like function” of the C terminal domain towards the N terminal domains which can be modulated by Ssa1/2 (cytosolic Hsp70)
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The Aconitase C-terminal domain is an independent dual targeting element.
Journal of molecular biology, 2011Co-Authors: Reut Ben-menachem, Neta Regev-rudzki, Ophry PinesAbstract:The tricarboxylic acid cycle enzyme Aconitase in yeast is a single translation product, which is dual targeted and distributed between the mitochondria and the cytosol by a unique mechanism involving reverse translocation. There is limited understanding regarding the precise mechanism of reverse translocation across the mitochondrial membranes. Here, we examined the contribution of the mature part of Aconitase to its dual targeting. We created a set of Aconitase mutants harboring two kinds of alterations: (1) point mutations or very small deletions in conserved sites and (2) systematic large deletions. These mutants were screened for their localization by a α-complementation assay, which revealed that the Aconitase fourth domain that is at the C-terminus (amino acids 517–778) is required for Aconitase distribution. Moreover, fusion of this C-terminal domain to mitochondria-targeted passenger proteins such as dihydrofolate reductase and orotidine-5′-phosphate decarboxylase, conferred dual localization on them. These results indicate that the Aconitase C-terminal domain is both necessary and sufficient for dual targeting, thereby functioning as an “independent signal”. In addition, the same C-terminal domain was shown to be necessary for Aconitase efficient posttranslational import into mitochondria.
Leslie C Costello - One of the best experts on this subject based on the ideXlab platform.
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Mitochondrial Aconitase and citrate metabolism in malignant and nonmalignant human prostate tissues
Molecular cancer, 2006Co-Authors: Keshav K. Singh, Renty B Franklin, Mohamed M. Desouki, Leslie C CostelloAbstract:Background In prostate cancer, normal citrate-producing glandular secretory epithelial cells undergo a metabolic transformation to malignant citrate-oxidizing cells. m-Aconitase is the critical step involved in this altered citrate metabolism that is essential to prostate malignancy. The limiting m-Aconitase activity in prostate epithelial cells could be the result of a decreased level of m-Aconitase enzyme and/or the inhibition of existing m-Aconitase. Earlier studies identified zinc as an inhibitor of m-Aconitase activity in prostate cells; and that the depletion of zinc in malignant cells is an important factor in this metabolic transformation. However, a possibility remains that an altered expression and level of m-Aconitase enzyme might also be involved in this metabolic transformation. To address this issue, the in situ level of m-Aconitase enzyme was determined by immunohistochemical analysis of prostate cancer tissue sections and malignant prostate cell lines.
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Mitochondrial Aconitase gene expression is regulated by testosterone and prolactin in prostate epithelial cells .
The Prostate, 2000Co-Authors: Leslie C Costello, Yiyan Liu, Jing Zou, Renty B FranklinAbstract:BACKGROUND m-Aconitase catalyzes the first step leading to the oxidation of citrate via the Krebs cycle. It is a constituitive enzyme in virtually all mammalian cells, found in excess, and is considered to be a regulatory or regulated enzyme. In contrast to these general relationships, prostate secretory epithelial cells possess a uniquely limiting mitochondrial (m-) Aconitase which minimizes the oxidation of citrate. This permits the unique prostate function of accumulating and secreting extraordinarily high levels of citrate. Previous animal studies demonstrated that testosterone and prolactin regulate the level of m-Aconitase specifically in citrate-producing prostate cells. The present studies were conducted to determine if testosterone and prolactin regulated the expression of the m-Aconitase gene in prostate cells, and to determine the effect of the hormones on human prostate cells. METHODS The studies were conducted with freshly prepared rat ventral, rat lateral, and pig prostate epithelial cells, and with the human malignant cell lines LNCaP and PC-3. The effects of 1 nM testosterone and 3 nM prolactin on the level of m-Aconitase mRNA and on the transcription rate of m-Aconitase were determined. RESULTS The studies revealed that both prolactin and testosterone increase the levels of m-Aconitase mRNA and the transcription rates of m-Aconitase in rat ventral prostate cells, pig prostate cells, and human malignant prostate cells (LNCaP and PC-3). In contrast, both hormones decreased the level of m-Aconitase mRNA and repressed m-Aconitase gene transcription in rat lateral prostate cells. The hormonal regulation of m-Aconitase corresponded with the levels of m-Aconitase enzyme, m-Aconitase activity, and citrate oxidation. CONCLUSIONS In addition to the constitutive expression of m-Aconitase, the m-Aconitase gene is testosterone- and prolactin-regulated in specifically targeted prostate cells. The hormonal regulation of m-Aconitase gene expression and biosynthesis of m-Aconitase provide a regulatory mechanism for the oxidation of citrate, and consequently, the level of net citrate production by prostate. The hormonally increased expression and biosynthesis of m-Aconitase in human malignant cells might be involved in the increased citrate oxidation associated with the development of true malignant cells in prostate cancer. Prostate 42:196–202, 2000. © 2000 Wiley-Liss, Inc.
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zinc causes a shift toward citrate at equilibrium of the m Aconitase reaction of prostate mitochondria
Journal of Inorganic Biochemistry, 2000Co-Authors: Leslie C Costello, Renty B Franklin, Claire M KennedyAbstract:Abstract Prostate secretory epithelial cells have the unique function and capability of accumulating and secreting extraordinarily high levels of citrate. To achieve this, these cells possess a uniquely limiting mitochondrial (m)-Aconitase activity that minimizes the oxidation of citrate via the Krebs cycle. The steady-state citrate/isocitrate ratio of mammalian tissues is generally maintained at about 10–11/1, independent of the concentration of citrate, which is the result of the chemical equilibrium reached in the presence of m-Aconitase. In contrast, the citrate/isocitrate ratio of prostate tissue is about 30–40/1. Zinc, which is also accumulated in prostate cells at much higher levels than in other cells, inhibits m-Aconitase activity thereby minimizing citrate oxidation. This current report is concerned with an effect of zinc on the equilibrium of the reaction catalyzed by m-Aconitase. Studies were conducted with mitochondrial extract preparations from rat ventral prostate epithelial cells. With citrate as the initial substrate, the addition of zinc (7–10 μM) to the prostate mitochondrial preparation resulted in a change in the citrate/isocitrate ratio at equilibrium from an average of 10.5/1 to 13.5/1. In contrast, the identical treatment of kidney mitochondrial preparations resulted in no zinc-induced change in the citrate/isocitrate ratio. When either cis -aconitate or isocitrate was employed as the initial substrate, the addition of zinc did not alter the citrate/isocitrate ratio of prostate or kidney preparations. Partial purification of the prostate preparation revealed that the prostate mitochondrial extract contained a putative protein (which we have designated as ‘citrate factor protein’) that is required for the zinc-induced increase in the citrate/isocitrate ratio. This novel effect of zinc provides another mechanism by which it is assured that the accumulation of citrate is maximized in citrate-producing prostate epithelial cells.
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zinc inhibition of mitochondrial Aconitase and its importance in citrate metabolism of prostate epithelial cells
Journal of Biological Chemistry, 1997Co-Authors: Leslie C Costello, Yiyan Liu, Renty B Franklin, Mary Claire KennedyAbstract:Prostate epithelial cells possess a uniquely limiting mitochondrial (m-) Aconitase activity that minimizes their ability to oxidize citrate. These cells also possess uniquely high cellular and mitochondrial zinc levels. Correlations among zinc, citrate, and m-Aconitase in prostate indicated that zinc might be an inhibitor of prostate m-Aconitase activity and citrate oxidation. The present studies reveal that zinc at near physiological levels inhibited m-Aconitase activity of mitochondrial sonicate preparations obtained from rat ventral prostate epithelial cells. Corresponding studies conducted with mitochondrial sonicates of rat kidney cells revealed that zinc also inhibited the kidney m-Aconitase activity. However the inhibitory effect of zinc was more sensitive with the prostate m-Aconitase activity. Zinc inhibition fit the competitive inhibitor model. The inhibitory effect of zinc occurred only with citrate as substrate and was specific for the citrate --> cis-aconitate reaction. Other cations (Ca2+, Mn2+, Cd2+) did not result in the inhibitory effects obtained with zinc. The presence of endogenous zinc inhibited the m-Aconitase activity of the prostate mitochondrial preparations. Kidney preparations that contain lower endogenous zinc levels exhibited no endogenous inhibition of m-Aconitase activity. Studies with pig prostate and seminal vesicle mitochondrial preparations also revealed that zinc was a competitive inhibitor against citrate of m-Aconitase activity. The effects of zinc on purified beef heart m-Aconitase verified the competitive inhibitor action of zinc. In contrast, zinc had no inhibitory effect on purified cytosolic Aconitase. These studies reveal for the first time that zinc is a specific inhibitor of m-Aconitase of mammalian cells. In prostate epithelial cells, in situ mitochondrial zinc levels inhibit m-Aconitase activity, which provides a mechanism by which citrate oxidation is limited.
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Testosterone and prolactin stimulation ofmitochondrial Aconitase in pig prostate epithelial cells
Urology, 1996Co-Authors: Leslie C Costello, Yiyan Liu, Renty B FranklinAbstract:Abstract Objectives . The function of the prostate gland in many animals, including humans, is to accumulate andsecrete large quantities of citrate. This function derives from the metabolic characteristics of the prostate secretory epithelial cells. These cells possess a uniquely limiting mitochondrial Aconitase (m-Aconitase) that minimizes citrate oxidation and thus permits citrate to accumulate. Unfortunately, the characteristics of prostate m-Aconitase and its manner of regulation have not been established. The hormones testosterone and prolactin, however, are significantly involved in regulating prostate citrate production. Thus it is reasonable to hypothesize that these hormones may be involved in the regulation of both m-Aconitase and citrate oxidation. Methods . Using freshly prepared pig prostate epithelial cells, we attempted to determine the effects oftestosterone and prolactin treatment on the level of m-Aconitase enzyme, on the level of m-Aconitase activity, and on citrate utilization. The epithelial cells were incubated for 3 hours with either testosterone (10 −9 M), prolactin (1 μg/mL), or vehicle (control). Results . Both hormone applications caused a marked increase in the level of m-Aconitase. In contrast, neitherhormone had any effect on the m-Aconitase level of pig seminal vesicle cells, which are also citrate-producing cells. Moreover, neither hormone had any effect on pyruvate dehydrogenase E1a. These findings suggest that testosterone and prolactin regulation of prostate m-Aconitase is a highly specific effect. Along with the increase in the level of m-Aconitase enzyme, both hormones also increased m-Aconitase activity and prostate-cell utilization of citrate. Conclusions . These studies demonstrate that testosterone and prolactin can regulate m-Aconitase and subsequent citrate oxidation of specific prostate epithelial cells. This unique Aconitase relationship is not observed in other mammalian cells.
Nicole Hansmeier - One of the best experts on this subject based on the ideXlab platform.
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Impact of ROS-Induced Damage of TCA Cycle Enzymes on Metabolism and Virulence of Salmonella enterica serovar Typhimurium
Frontiers Media S.A., 2019Co-Authors: Janina Noster, Marcus Persicke, Tzu-chiao Chao, Lena Krone, Bianca Heppner, Michael Hensel, Nicole HansmeierAbstract:Salmonella enterica serovar Typhimurium (STM) is exposed to reactive oxygen species (ROS) originating from aerobic respiration, antibiotic treatment, and the oxidative burst occurring inside the Salmonella-containing vacuole (SCV) within host cells. ROS damage cellular compounds, thereby impairing bacterial viability and inducing cell death. Proteins containing iron–sulfur (Fe–S) clusters are particularly sensitive and become non-functional upon oxidation. Comprising five enzymes with Fe–S clusters, the TCA cycle is a pathway most sensitive toward ROS. To test the impact of ROS-mediated metabolic perturbations on bacterial physiology, we analyzed the proteomic and metabolic profile of STM deficient in both cytosolic superoxide dismutases (ΔsodAB). Incapable of detoxifying superoxide anions (SOA), endogenously generated SOA accumulate during growth. ΔsodAB showed reduced abundance of Aconitases, leading to a metabolic profile similar to that of an Aconitase-deficient strain (ΔacnAB). Furthermore, we determined a decreased expression of acnA in STM ΔsodAB. While intracellular proliferation in RAW264.7 macrophages and survival of methyl viologen treatment were not reduced for STM ΔacnAB, proteomic profiling revealed enhanced stress response. We conclude that ROS-mediated reduced expression and damage of Aconitase does not impair bacterial viability or virulence, but might increase ROS amounts in STM, which reinforces the bactericidal effects of antibiotic treatment and immune responses of the host
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Image_5_Impact of ROS-Induced Damage of TCA Cycle Enzymes on Metabolism and Virulence of Salmonella enterica serovar Typhimurium.TIF
2019Co-Authors: Janina Noster, Marcus Persicke, Tzu-chiao Chao, Lena Krone, Bianca Heppner, Michael Hensel, Nicole HansmeierAbstract:Salmonella enterica serovar Typhimurium (STM) is exposed to reactive oxygen species (ROS) originating from aerobic respiration, antibiotic treatment, and the oxidative burst occurring inside the Salmonella-containing vacuole (SCV) within host cells. ROS damage cellular compounds, thereby impairing bacterial viability and inducing cell death. Proteins containing iron–sulfur (Fe–S) clusters are particularly sensitive and become non-functional upon oxidation. Comprising five enzymes with Fe–S clusters, the TCA cycle is a pathway most sensitive toward ROS. To test the impact of ROS-mediated metabolic perturbations on bacterial physiology, we analyzed the proteomic and metabolic profile of STM deficient in both cytosolic superoxide dismutases (ΔsodAB). Incapable of detoxifying superoxide anions (SOA), endogenously generated SOA accumulate during growth. ΔsodAB showed reduced abundance of Aconitases, leading to a metabolic profile similar to that of an Aconitase-deficient strain (ΔacnAB). Furthermore, we determined a decreased expression of acnA in STM ΔsodAB. While intracellular proliferation in RAW264.7 macrophages and survival of methyl viologen treatment were not reduced for STM ΔacnAB, proteomic profiling revealed enhanced stress response. We conclude that ROS-mediated reduced expression and damage of Aconitase does not impair bacterial viability or virulence, but might increase ROS amounts in STM, which reinforces the bactericidal effects of antibiotic treatment and immune responses of the host.
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Table_3_Impact of ROS-Induced Damage of TCA Cycle Enzymes on Metabolism and Virulence of Salmonella enterica serovar Typhimurium.XLSX
2019Co-Authors: Janina Noster, Marcus Persicke, Tzu-chiao Chao, Lena Krone, Bianca Heppner, Michael Hensel, Nicole HansmeierAbstract:Salmonella enterica serovar Typhimurium (STM) is exposed to reactive oxygen species (ROS) originating from aerobic respiration, antibiotic treatment, and the oxidative burst occurring inside the Salmonella-containing vacuole (SCV) within host cells. ROS damage cellular compounds, thereby impairing bacterial viability and inducing cell death. Proteins containing iron–sulfur (Fe–S) clusters are particularly sensitive and become non-functional upon oxidation. Comprising five enzymes with Fe–S clusters, the TCA cycle is a pathway most sensitive toward ROS. To test the impact of ROS-mediated metabolic perturbations on bacterial physiology, we analyzed the proteomic and metabolic profile of STM deficient in both cytosolic superoxide dismutases (ΔsodAB). Incapable of detoxifying superoxide anions (SOA), endogenously generated SOA accumulate during growth. ΔsodAB showed reduced abundance of Aconitases, leading to a metabolic profile similar to that of an Aconitase-deficient strain (ΔacnAB). Furthermore, we determined a decreased expression of acnA in STM ΔsodAB. While intracellular proliferation in RAW264.7 macrophages and survival of methyl viologen treatment were not reduced for STM ΔacnAB, proteomic profiling revealed enhanced stress response. We conclude that ROS-mediated reduced expression and damage of Aconitase does not impair bacterial viability or virulence, but might increase ROS amounts in STM, which reinforces the bactericidal effects of antibiotic treatment and immune responses of the host.
Renty B Franklin - One of the best experts on this subject based on the ideXlab platform.
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Mitochondrial Aconitase and citrate metabolism in malignant and nonmalignant human prostate tissues
Molecular cancer, 2006Co-Authors: Keshav K. Singh, Renty B Franklin, Mohamed M. Desouki, Leslie C CostelloAbstract:Background In prostate cancer, normal citrate-producing glandular secretory epithelial cells undergo a metabolic transformation to malignant citrate-oxidizing cells. m-Aconitase is the critical step involved in this altered citrate metabolism that is essential to prostate malignancy. The limiting m-Aconitase activity in prostate epithelial cells could be the result of a decreased level of m-Aconitase enzyme and/or the inhibition of existing m-Aconitase. Earlier studies identified zinc as an inhibitor of m-Aconitase activity in prostate cells; and that the depletion of zinc in malignant cells is an important factor in this metabolic transformation. However, a possibility remains that an altered expression and level of m-Aconitase enzyme might also be involved in this metabolic transformation. To address this issue, the in situ level of m-Aconitase enzyme was determined by immunohistochemical analysis of prostate cancer tissue sections and malignant prostate cell lines.
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Mitochondrial Aconitase gene expression is regulated by testosterone and prolactin in prostate epithelial cells .
The Prostate, 2000Co-Authors: Leslie C Costello, Yiyan Liu, Jing Zou, Renty B FranklinAbstract:BACKGROUND m-Aconitase catalyzes the first step leading to the oxidation of citrate via the Krebs cycle. It is a constituitive enzyme in virtually all mammalian cells, found in excess, and is considered to be a regulatory or regulated enzyme. In contrast to these general relationships, prostate secretory epithelial cells possess a uniquely limiting mitochondrial (m-) Aconitase which minimizes the oxidation of citrate. This permits the unique prostate function of accumulating and secreting extraordinarily high levels of citrate. Previous animal studies demonstrated that testosterone and prolactin regulate the level of m-Aconitase specifically in citrate-producing prostate cells. The present studies were conducted to determine if testosterone and prolactin regulated the expression of the m-Aconitase gene in prostate cells, and to determine the effect of the hormones on human prostate cells. METHODS The studies were conducted with freshly prepared rat ventral, rat lateral, and pig prostate epithelial cells, and with the human malignant cell lines LNCaP and PC-3. The effects of 1 nM testosterone and 3 nM prolactin on the level of m-Aconitase mRNA and on the transcription rate of m-Aconitase were determined. RESULTS The studies revealed that both prolactin and testosterone increase the levels of m-Aconitase mRNA and the transcription rates of m-Aconitase in rat ventral prostate cells, pig prostate cells, and human malignant prostate cells (LNCaP and PC-3). In contrast, both hormones decreased the level of m-Aconitase mRNA and repressed m-Aconitase gene transcription in rat lateral prostate cells. The hormonal regulation of m-Aconitase corresponded with the levels of m-Aconitase enzyme, m-Aconitase activity, and citrate oxidation. CONCLUSIONS In addition to the constitutive expression of m-Aconitase, the m-Aconitase gene is testosterone- and prolactin-regulated in specifically targeted prostate cells. The hormonal regulation of m-Aconitase gene expression and biosynthesis of m-Aconitase provide a regulatory mechanism for the oxidation of citrate, and consequently, the level of net citrate production by prostate. The hormonally increased expression and biosynthesis of m-Aconitase in human malignant cells might be involved in the increased citrate oxidation associated with the development of true malignant cells in prostate cancer. Prostate 42:196–202, 2000. © 2000 Wiley-Liss, Inc.
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zinc causes a shift toward citrate at equilibrium of the m Aconitase reaction of prostate mitochondria
Journal of Inorganic Biochemistry, 2000Co-Authors: Leslie C Costello, Renty B Franklin, Claire M KennedyAbstract:Abstract Prostate secretory epithelial cells have the unique function and capability of accumulating and secreting extraordinarily high levels of citrate. To achieve this, these cells possess a uniquely limiting mitochondrial (m)-Aconitase activity that minimizes the oxidation of citrate via the Krebs cycle. The steady-state citrate/isocitrate ratio of mammalian tissues is generally maintained at about 10–11/1, independent of the concentration of citrate, which is the result of the chemical equilibrium reached in the presence of m-Aconitase. In contrast, the citrate/isocitrate ratio of prostate tissue is about 30–40/1. Zinc, which is also accumulated in prostate cells at much higher levels than in other cells, inhibits m-Aconitase activity thereby minimizing citrate oxidation. This current report is concerned with an effect of zinc on the equilibrium of the reaction catalyzed by m-Aconitase. Studies were conducted with mitochondrial extract preparations from rat ventral prostate epithelial cells. With citrate as the initial substrate, the addition of zinc (7–10 μM) to the prostate mitochondrial preparation resulted in a change in the citrate/isocitrate ratio at equilibrium from an average of 10.5/1 to 13.5/1. In contrast, the identical treatment of kidney mitochondrial preparations resulted in no zinc-induced change in the citrate/isocitrate ratio. When either cis -aconitate or isocitrate was employed as the initial substrate, the addition of zinc did not alter the citrate/isocitrate ratio of prostate or kidney preparations. Partial purification of the prostate preparation revealed that the prostate mitochondrial extract contained a putative protein (which we have designated as ‘citrate factor protein’) that is required for the zinc-induced increase in the citrate/isocitrate ratio. This novel effect of zinc provides another mechanism by which it is assured that the accumulation of citrate is maximized in citrate-producing prostate epithelial cells.
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zinc inhibition of mitochondrial Aconitase and its importance in citrate metabolism of prostate epithelial cells
Journal of Biological Chemistry, 1997Co-Authors: Leslie C Costello, Yiyan Liu, Renty B Franklin, Mary Claire KennedyAbstract:Prostate epithelial cells possess a uniquely limiting mitochondrial (m-) Aconitase activity that minimizes their ability to oxidize citrate. These cells also possess uniquely high cellular and mitochondrial zinc levels. Correlations among zinc, citrate, and m-Aconitase in prostate indicated that zinc might be an inhibitor of prostate m-Aconitase activity and citrate oxidation. The present studies reveal that zinc at near physiological levels inhibited m-Aconitase activity of mitochondrial sonicate preparations obtained from rat ventral prostate epithelial cells. Corresponding studies conducted with mitochondrial sonicates of rat kidney cells revealed that zinc also inhibited the kidney m-Aconitase activity. However the inhibitory effect of zinc was more sensitive with the prostate m-Aconitase activity. Zinc inhibition fit the competitive inhibitor model. The inhibitory effect of zinc occurred only with citrate as substrate and was specific for the citrate --> cis-aconitate reaction. Other cations (Ca2+, Mn2+, Cd2+) did not result in the inhibitory effects obtained with zinc. The presence of endogenous zinc inhibited the m-Aconitase activity of the prostate mitochondrial preparations. Kidney preparations that contain lower endogenous zinc levels exhibited no endogenous inhibition of m-Aconitase activity. Studies with pig prostate and seminal vesicle mitochondrial preparations also revealed that zinc was a competitive inhibitor against citrate of m-Aconitase activity. The effects of zinc on purified beef heart m-Aconitase verified the competitive inhibitor action of zinc. In contrast, zinc had no inhibitory effect on purified cytosolic Aconitase. These studies reveal for the first time that zinc is a specific inhibitor of m-Aconitase of mammalian cells. In prostate epithelial cells, in situ mitochondrial zinc levels inhibit m-Aconitase activity, which provides a mechanism by which citrate oxidation is limited.
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Testosterone and prolactin stimulation ofmitochondrial Aconitase in pig prostate epithelial cells
Urology, 1996Co-Authors: Leslie C Costello, Yiyan Liu, Renty B FranklinAbstract:Abstract Objectives . The function of the prostate gland in many animals, including humans, is to accumulate andsecrete large quantities of citrate. This function derives from the metabolic characteristics of the prostate secretory epithelial cells. These cells possess a uniquely limiting mitochondrial Aconitase (m-Aconitase) that minimizes citrate oxidation and thus permits citrate to accumulate. Unfortunately, the characteristics of prostate m-Aconitase and its manner of regulation have not been established. The hormones testosterone and prolactin, however, are significantly involved in regulating prostate citrate production. Thus it is reasonable to hypothesize that these hormones may be involved in the regulation of both m-Aconitase and citrate oxidation. Methods . Using freshly prepared pig prostate epithelial cells, we attempted to determine the effects oftestosterone and prolactin treatment on the level of m-Aconitase enzyme, on the level of m-Aconitase activity, and on citrate utilization. The epithelial cells were incubated for 3 hours with either testosterone (10 −9 M), prolactin (1 μg/mL), or vehicle (control). Results . Both hormone applications caused a marked increase in the level of m-Aconitase. In contrast, neitherhormone had any effect on the m-Aconitase level of pig seminal vesicle cells, which are also citrate-producing cells. Moreover, neither hormone had any effect on pyruvate dehydrogenase E1a. These findings suggest that testosterone and prolactin regulation of prostate m-Aconitase is a highly specific effect. Along with the increase in the level of m-Aconitase enzyme, both hormones also increased m-Aconitase activity and prostate-cell utilization of citrate. Conclusions . These studies demonstrate that testosterone and prolactin can regulate m-Aconitase and subsequent citrate oxidation of specific prostate epithelial cells. This unique Aconitase relationship is not observed in other mammalian cells.
Abraham L. Sonenshein - One of the best experts on this subject based on the ideXlab platform.
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Bacillus subtilis Aconitase Is Required for Efficient Late-Sporulation Gene Expression
Journal of bacteriology, 2006Co-Authors: Alisa W. Serio, Kieran B. Pechter, Abraham L. SonensheinAbstract:Bacillus subtilis Aconitase, encoded by the citB gene, is homologous to the bifunctional eukaryotic protein IRP-1 (iron regulatory protein 1). Like IRP-1, B. subtilis Aconitase is both an enzyme and an RNA binding protein. In an attempt to separate the two activities of Aconitase, the C-terminal region of the B. subtilis citB gene product was mutagenized. The resulting strain had high catalytic activity but was defective in sporulation. The defect was at a late stage of sporulation, specifically affecting expression of sigmaK-dependent genes, many of which are important for spore coat assembly and require transcriptional activation by GerE. Accumulation of gerE mRNA and GerE protein was delayed in the Aconitase mutant strain. Pure B. subtilis Aconitase bound to the 3' untranslated region of gerE mRNA in in vitro gel mobility shift assays, strongly suggesting that Aconitase RNA binding activity may stabilize gerE mRNA in order to allow efficient GerE synthesis and proper timing of spore coat assembly.
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Expression of Yeast Mitochondrial Aconitase in Bacillus subtilis
Journal of bacteriology, 2006Co-Authors: Alisa W. Serio, Abraham L. SonensheinAbstract:Expression of yeast mitochondrial Aconitase (Aco1) in a Bacillus subtilis Aconitase null mutant restored Aconitase activity and glutamate prototrophy but only partially restored sporulation. Late sporulation gene expression in the Aco1-expressing strain was delayed.
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Bacillus subtilis Aconitase is an RNA-binding protein
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Claudia Alén, Abraham L. SonensheinAbstract:The Aconitase protein of Bacillus subtilis was able to bind specifically to sequences resembling the iron response elements (IREs) found in eukaryotic mRNAs. The sequences bound include the rabbit ferritin IRE and IRE-like sequences in the B. subtilis operons that encode the major cytochrome oxidase and an iron uptake system. IRE binding activity was affected by the availability of iron both in vivo and in vitro. In eukaryotic cells, Aconitase-like proteins regulate translation and stability of iron metabolism mRNAs in response to iron availability. A mutant strain of B. subtilis that produces an enzymatically inactive Aconitase that was still able to bind RNA sporulated 40× more efficiently than did an Aconitase null mutant, suggesting that a nonenzymatic activity of Aconitase is important for sporulation. The results support the idea that bacterial Aconitases, like their eukaryotic homologs, are bifunctional proteins, showing Aconitase activity in the presence of iron and RNA binding activity when cells are iron-deprived.
