The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Peter Setlow - One of the best experts on this subject based on the ideXlab platform.
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the effects of Heat Activation on bacillus spore germination with nutrients or under high pressure with or without various germination proteins
Applied and Environmental Microbiology, 2015Co-Authors: Stephanie Luu, Jose Cruzmora, Barbara Setlow, Florence E Feeherry, Christopher J Doona, Peter SetlowAbstract:Nutrient germination of spores of Bacillus species occurs through germinant receptors (GRs) in spores' inner membrane (IM) in a process stimulated by sublethal Heat Activation. Bacillus subtilis spores maximum germination rates via different GRs required different 75 °C Heat Activation times: 15 min for l-valine germination via the GerA GR and 4 h for germination with the L-asparagine-glucose-fructose-K(+) mixture via the GerB and GerK GRs, with GerK requiring the most Heat Activation. In some cases, optimal Heat Activation decreased nutrient concentrations for half-maximal germination rates. Germination of spores via various GRs by high pressure (HP) of 150 MPa exhibited Heat Activation requirements similar to those of nutrient germination, and the loss of the GerD protein, required for optimal GR function, did not eliminate Heat Activation requirements for maximal germination rates. These results are consistent with Heat Activation acting primarily on GRs. However, (i) Heat Activation had no effects on GR or GerD protein conformation, as probed by biotinylation by an external reagent; (ii) spores prepared at low and high temperatures that affect spores' IM properties exhibited large differences in Heat Activation requirements for nutrient germination; and (iii) spore germination by 550 MPa of HP was also affected by Heat Activation, but the effects were relatively GR independent. The last results are consistent with Heat Activation affecting spores' IM and only indirectly affecting GRs. The 150- and 550-MPa HP germinations of Bacillus amyloliquefaciens spores, a potential surrogate for Clostridium botulinum spores in HP treatments of foods, were also stimulated by Heat Activation.
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factors affecting variability in time between addition of nutrient germinants and rapid dipicolinic acid release during germination of spores of bacillus species
Journal of Bacteriology, 2010Co-Authors: Pengfei Zhang, Will Garner, Peter SetlowAbstract:The simultaneous nutrient germination of hundreds of individual wild-type spores of three Bacillus species and a number of Bacillus subtilis strains has been measured by two new methods, and rates of release of the great majority of the large pool of dipicolinic acid (DPA) from individual spores of B. subtilis strains has been measured by Raman spectroscopy with laser tweezers. The results from these analyses and published data have allowed a number of significant conclusions about the germination of spores of Bacillus species as follows. (i) The time needed for release of the great majority of a Bacillus spore’s DPA once rapid DPA release had begun (Trelease) during nutrient germination was independent of the concentration of nutrient germinant used, the level of the germinant receptors (GRs) that recognize nutrient germinants used and Heat Activation prior to germination. Values for Trelease were generally 0.5 to 3 min at 25 to 37°C for individual wild-type spores. (ii) Despite the conclusion above, germination of individual spores in populations was very heterogeneous, with some spores in wild-type populations completing germination >15-fold slower than others. (iii) The major factor in the heterogeneity in germination of individual spores in populations was the highly variable lag time, Tlag, between mixing spores with nutrient germinants and the beginning of Trelease. (iv) A number of factors decrease spores’ Tlag values including Heat Activation, increased levels of GRs/spore, and higher levels of nutrient germinants. These latter factors appear to affect the level of activated GRs/spore during nutrient germination. (v) The conclusions above lead to the simple prediction that a major factor causing heterogeneity in Bacillus spore germination is the number of functional GRs in individual spores, a number that presumably varies significantly between spores in populations.
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studies of the commitment step in the germination of spores of bacillus species
Journal of Bacteriology, 2010Co-Authors: Xuan Yi, Peter SetlowAbstract:Spores of Bacillus species are said to be committed when they continue through nutrient germination even when germinants are removed or their binding to spores' nutrient germinant receptors (GRs) is both reversed and inhibited. Measurement of commitment and the subsequent release of dipicolinic acid (DPA) during nutrient germination of spores of Bacillus cereus and Bacillus subtilis showed that Heat Activation, increased nutrient germinant concentrations, and higher average levels of GRs/spore significantly decreased the times needed for commitment, as well as lag times between commitment and DPA release. These lag times were also decreased dramatically by the action of one of the spores' two redundant cortex lytic enzymes (CLEs), CwlJ, but not by the other CLE, SleB, and CwlJ action did not affect the timing of commitment. The timing of commitment and the lag time between commitment and DPA release were also dependent on the specific GR activated to cause spore germination. For spore populations, the lag times between commitment and DPA release were increased significantly in spores that germinated late compared to those that germinated early, and individual spores that germinated late may have had lower appropriate GR levels/spore than spores that germinated early. These findings together provide new insight into the commitment step in spore germination and suggest several factors that may contribute to the large heterogeneity among the timings of various events in the germination of individual spores in spore populations.
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superdormant spores of bacillus species germinate normally with high pressure peptidoglycan fragments and bryostatin
Journal of Bacteriology, 2010Co-Authors: Jie Wei, Sonali Pal-ghosh, Ishita M Shah, Jonathan Dworkin, Dallas G Hoover, Peter SetlowAbstract:Superdormant spores of Bacillus cereus and Bacillus subtilis germinated just as well as dormant spores with pressures of 150 or 500 MPa and with or without Heat Activation. Superdormant B. subtilis spores also germinated as well as dormant spores with peptidoglycan fragments or bryostatin, a Ser/Thr protein kinase activator.
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superdormant spores of bacillus species have elevated wet Heat resistance and temperature requirements for Heat Activation
Journal of Bacteriology, 2009Co-Authors: Sonali Pal-ghosh, Pengfei Zhang, Peter SetlowAbstract:Purified superdormant spores of Bacillus cereus, B. megaterium, and B. subtilis isolated after optimal Heat Activation of dormant spores and subsequent germination with inosine, d-glucose, or l-valine, respectively, germinate very poorly with the original germinants used to remove dormant spores from spore populations, thus allowing isolation of the superdormant spores, and even with alternate germinants. However, these superdormant spores exhibited significant germination with the original or alternate germinants if the spores were Heat activated at temperatures 8 to 15 degrees C higher than the optimal temperatures for the original dormant spores, although the levels of superdormant spore germination were not as great as those of dormant spores. Use of mixtures of original and alternate germinants lowered the Heat Activation temperature optima for both dormant and superdormant spores. The superdormant spores had higher wet-Heat resistance and lower core water content than the original dormant spore populations, and the environment of dipicolinic acid in the core of superdormant spores as determined by Raman spectroscopy of individual spores differed from that in dormant spores. These results provide new information about the germination, Heat Activation optima, and wet-Heat resistance of superdormant spores and the heterogeneity in these properties between individual members of dormant spore populations.
Sonali Pal-ghosh - One of the best experts on this subject based on the ideXlab platform.
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superdormant spores of bacillus species germinate normally with high pressure peptidoglycan fragments and bryostatin
Journal of Bacteriology, 2010Co-Authors: Jie Wei, Sonali Pal-ghosh, Ishita M Shah, Jonathan Dworkin, Dallas G Hoover, Peter SetlowAbstract:Superdormant spores of Bacillus cereus and Bacillus subtilis germinated just as well as dormant spores with pressures of 150 or 500 MPa and with or without Heat Activation. Superdormant B. subtilis spores also germinated as well as dormant spores with peptidoglycan fragments or bryostatin, a Ser/Thr protein kinase activator.
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superdormant spores of bacillus species have elevated wet Heat resistance and temperature requirements for Heat Activation
Journal of Bacteriology, 2009Co-Authors: Sonali Pal-ghosh, Pengfei Zhang, Peter SetlowAbstract:Purified superdormant spores of Bacillus cereus, B. megaterium, and B. subtilis isolated after optimal Heat Activation of dormant spores and subsequent germination with inosine, d-glucose, or l-valine, respectively, germinate very poorly with the original germinants used to remove dormant spores from spore populations, thus allowing isolation of the superdormant spores, and even with alternate germinants. However, these superdormant spores exhibited significant germination with the original or alternate germinants if the spores were Heat activated at temperatures 8 to 15 degrees C higher than the optimal temperatures for the original dormant spores, although the levels of superdormant spore germination were not as great as those of dormant spores. Use of mixtures of original and alternate germinants lowered the Heat Activation temperature optima for both dormant and superdormant spores. The superdormant spores had higher wet-Heat resistance and lower core water content than the original dormant spore populations, and the environment of dipicolinic acid in the core of superdormant spores as determined by Raman spectroscopy of individual spores differed from that in dormant spores. These results provide new information about the germination, Heat Activation optima, and wet-Heat resistance of superdormant spores and the heterogeneity in these properties between individual members of dormant spore populations.
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isolation and characterization of superdormant spores of bacillus species
Journal of Bacteriology, 2009Co-Authors: Sonali Pal-ghosh, Peter SetlowAbstract:Superdormant spores of Bacillus subtilis and Bacillus megaterium were isolated in 4 to 12% yields following germination with high nutrient levels that activated one or two germinant receptors. These superdormant spores did not germinate with the initial nutrients or those that stimulated other germinant receptors, and the superdormant spores' defect was not genetic. The superdormant spores did, however, germinate with Ca2+-dipicolinic acid or dodecylamine. Although these superdormant spores did not germinate with high levels of nutrients that activated one or two nutrient germinant receptors, they germinated with nutrient mixtures that activated more receptors, and using high levels of nutrient mixtures activating more germinant receptors decreased superdormant spore yields. The use of moderate nutrient levels to isolate superdormant spores increased their yields; the resultant spores germinated poorly with the initial moderate nutrient concentrations, but they germinated well with high nutrient concentrations. These findings suggest that the levels of superdormant spores in populations depend on the germination conditions used, with fewer superdormant spores isolated when better germination conditions are used. These findings further suggest that superdormant spores require an increased signal for triggering spore germination compared to most spores in populations. One factor determining whether a spore is superdormant is its level of germinant receptors, since spore populations with higher levels of germinant receptors yielded lower levels of superdormant spores. A second important factor may be Heat Activation of spore populations, since yields of superdormant spores from non-Heat-activated spore populations were higher than those from optimally activated spores.
Jie Zheng - One of the best experts on this subject based on the ideXlab platform.
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a specialized pore turret in the mammalian cation channel trpv1 is responsible for distinct and species specific Heat Activation thresholds
Journal of Biological Chemistry, 2020Co-Authors: Yuhua Tian, Jie Zheng, Kewei Wang, Zhihao Yao, Longhui Chai, Shilong YangAbstract:The transient receptor potential vanilloid 1 (TRPV1) channel is a Heat-activated cation channel that plays a crucial role in ambient temperature detection and thermal homeostasis. Although several structural features of TRPV1 have been shown to be involved in Heat-induced Activation of the gating process, the physiological significance of only a few of these key elements has been evaluated in an evolutionary context. Here, using transient expression in HEK293 cells, electrophysiological recordings, and molecular modeling, we show that the pore turret contains both structural and functional determinants that set the Heat Activation thresholds of distinct TRPV1 orthologs in mammals whose body temperatures fluctuate widely. We found that TRPV1 from the bat Carollia brevicauda exhibits a lower threshold temperature of channel Activation than does its human ortholog and three bat-specific amino acid substitutions located in the pore turret are sufficient to determine this threshold temperature. Furthermore, the structure of the TRPV1 pore turret appears to be of physiological and evolutionary significance for differentiating the Heat-activated threshold among species-specific TRPV1 orthologs. These findings support a role for the TRPV1 pore turret in tuning the Heat-activated threshold, and they suggest that its evolution was driven by adaption to specific physiological traits among mammals exposed to variable temperatures.
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a pain inducing centipede toxin targets the Heat Activation machinery of nociceptor trpv1
Nature Communications, 2015Co-Authors: Jie Zheng, Shilong Yang, Fan Yang, Jing Hong, Bowen Li, Mingqiang Rong, Vladimir Yarovyarovoy, Kewei WangAbstract:The capsaicin receptor TRPV1 ion channel is a polymodal nociceptor that responds to Heat with exquisite sensitivity through an unknown mechanism. Here we report the identification of a novel toxin, RhTx, from the venom of the Chinese red-headed centipede that potently activates TRPV1 to produce excruciating pain. RhTx is a 27-amino-acid small peptide that forms a compact polarized molecule with very rapid binding kinetics and high affinity for TRPV1. We show that RhTx targets the channel's Heat Activation machinery to cause powerful Heat Activation at body temperature. The RhTx-TRPV1 interaction is mediated by the toxin's highly charged C terminus, which associates tightly to the charge-rich outer pore region of the channel where it can directly interact with the pore helix and turret. These findings demonstrate that RhTx binding to the outer pore can induce TRPV1 Heat Activation, therefore providing crucial new structural information on the Heat Activation machinery.
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selective disruption of high sensitivity Heat Activation but not capsaicin Activation of trpv1 channels by pore turret mutations
The Journal of General Physiology, 2012Co-Authors: Yuanyuan Cui, Fan Yang, Vladimir Yarovyarovoy, Kewei Wang, Xu Cao, Jie ZhengAbstract:The capsaicin receptor transient receptor potential vanilloid (TRPV)1 is a highly Heat-sensitive ion channel. Although chemical Activation and Heat Activation of TRPV1 elicit similar pungent, painful sensation, the molecular mechanism underlying synergistic Activation remains mysterious. In particular, where the temperature sensor is located and whether Heat and capsaicin share a common Activation pathway are debated. To address these fundamental issues, we searched for channel mutations that selectively affected one form of Activation. We found that deletion of the first 10 amino acids of the pore turret significantly reduced the Heat response amplitude and shifted the Heat Activation threshold, whereas capsaicin Activation remained unchanged. Removing larger portions of the turret disrupted channel function. Introducing an artificial sequence to replace the deleted region restored sensitive capsaicin Activation in these nonfunctional channels. The Heat Activation, however, remained significantly impaired, with the current exhibiting diminishing Heat sensitivity to a level indistinguishable from that of a voltage-gated potassium channel, Kv7.4. Our results demonstrate that Heat and capsaicin Activation of TRPV1 are structurally and mechanistically distinct processes, and the pore turret is an indispensible channel structure involved in the Heat Activation process but is not part of the capsaicin Activation pathway. Synergistic effect of Heat and capsaicin on TRPV1 Activation may originate from convergence of the two pathways on a common Activation gate.
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Heat Activation of trpv channels
Biophysical Journal, 2012Co-Authors: Jie ZhengAbstract:Activation of TRPV1-4 channels is exquisitely Heat-sensitive due to large and balanced changes in entropy and enthalpy. Identification of channel structures that underlie these changes is thus the prerequisite for understanding the molecular mechanism of Heat Activation. We approach this goal through a combination of methods. We use improved Heating methods to accurately control temperature-dependent Activation of wildtype channel and mutants which exhibit altered gating behavior, use structural analysis to guide our search for critical domains, and use site-directed fluorescence recordings to monitor conformational changes. For capsaicin receptor TRPV1, Heat Activation appears to be carried out by the central pore domain, while capsaicin is known to activate the channel by binding to the peripheral S2-S4 region. Structurally and mechanistically separated Heat and agonist Activation pathways suggest the possibility to selectively manipulate each process in this pain sensor for pharmaceutical purposes. The Heat Activation process appears to be preserved among TRPV1-3 channels.
Pengfei Zhang - One of the best experts on this subject based on the ideXlab platform.
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factors affecting variability in time between addition of nutrient germinants and rapid dipicolinic acid release during germination of spores of bacillus species
Journal of Bacteriology, 2010Co-Authors: Pengfei Zhang, Will Garner, Peter SetlowAbstract:The simultaneous nutrient germination of hundreds of individual wild-type spores of three Bacillus species and a number of Bacillus subtilis strains has been measured by two new methods, and rates of release of the great majority of the large pool of dipicolinic acid (DPA) from individual spores of B. subtilis strains has been measured by Raman spectroscopy with laser tweezers. The results from these analyses and published data have allowed a number of significant conclusions about the germination of spores of Bacillus species as follows. (i) The time needed for release of the great majority of a Bacillus spore’s DPA once rapid DPA release had begun (Trelease) during nutrient germination was independent of the concentration of nutrient germinant used, the level of the germinant receptors (GRs) that recognize nutrient germinants used and Heat Activation prior to germination. Values for Trelease were generally 0.5 to 3 min at 25 to 37°C for individual wild-type spores. (ii) Despite the conclusion above, germination of individual spores in populations was very heterogeneous, with some spores in wild-type populations completing germination >15-fold slower than others. (iii) The major factor in the heterogeneity in germination of individual spores in populations was the highly variable lag time, Tlag, between mixing spores with nutrient germinants and the beginning of Trelease. (iv) A number of factors decrease spores’ Tlag values including Heat Activation, increased levels of GRs/spore, and higher levels of nutrient germinants. These latter factors appear to affect the level of activated GRs/spore during nutrient germination. (v) The conclusions above lead to the simple prediction that a major factor causing heterogeneity in Bacillus spore germination is the number of functional GRs in individual spores, a number that presumably varies significantly between spores in populations.
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superdormant spores of bacillus species have elevated wet Heat resistance and temperature requirements for Heat Activation
Journal of Bacteriology, 2009Co-Authors: Sonali Pal-ghosh, Pengfei Zhang, Peter SetlowAbstract:Purified superdormant spores of Bacillus cereus, B. megaterium, and B. subtilis isolated after optimal Heat Activation of dormant spores and subsequent germination with inosine, d-glucose, or l-valine, respectively, germinate very poorly with the original germinants used to remove dormant spores from spore populations, thus allowing isolation of the superdormant spores, and even with alternate germinants. However, these superdormant spores exhibited significant germination with the original or alternate germinants if the spores were Heat activated at temperatures 8 to 15 degrees C higher than the optimal temperatures for the original dormant spores, although the levels of superdormant spore germination were not as great as those of dormant spores. Use of mixtures of original and alternate germinants lowered the Heat Activation temperature optima for both dormant and superdormant spores. The superdormant spores had higher wet-Heat resistance and lower core water content than the original dormant spore populations, and the environment of dipicolinic acid in the core of superdormant spores as determined by Raman spectroscopy of individual spores differed from that in dormant spores. These results provide new information about the germination, Heat Activation optima, and wet-Heat resistance of superdormant spores and the heterogeneity in these properties between individual members of dormant spore populations.
Shilong Yang - One of the best experts on this subject based on the ideXlab platform.
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a specialized pore turret in the mammalian cation channel trpv1 is responsible for distinct and species specific Heat Activation thresholds
Journal of Biological Chemistry, 2020Co-Authors: Yuhua Tian, Jie Zheng, Kewei Wang, Zhihao Yao, Longhui Chai, Shilong YangAbstract:The transient receptor potential vanilloid 1 (TRPV1) channel is a Heat-activated cation channel that plays a crucial role in ambient temperature detection and thermal homeostasis. Although several structural features of TRPV1 have been shown to be involved in Heat-induced Activation of the gating process, the physiological significance of only a few of these key elements has been evaluated in an evolutionary context. Here, using transient expression in HEK293 cells, electrophysiological recordings, and molecular modeling, we show that the pore turret contains both structural and functional determinants that set the Heat Activation thresholds of distinct TRPV1 orthologs in mammals whose body temperatures fluctuate widely. We found that TRPV1 from the bat Carollia brevicauda exhibits a lower threshold temperature of channel Activation than does its human ortholog and three bat-specific amino acid substitutions located in the pore turret are sufficient to determine this threshold temperature. Furthermore, the structure of the TRPV1 pore turret appears to be of physiological and evolutionary significance for differentiating the Heat-activated threshold among species-specific TRPV1 orthologs. These findings support a role for the TRPV1 pore turret in tuning the Heat-activated threshold, and they suggest that its evolution was driven by adaption to specific physiological traits among mammals exposed to variable temperatures.
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a pain inducing centipede toxin targets the Heat Activation machinery of nociceptor trpv1
Nature Communications, 2015Co-Authors: Jie Zheng, Shilong Yang, Fan Yang, Jing Hong, Bowen Li, Mingqiang Rong, Vladimir Yarovyarovoy, Kewei WangAbstract:The capsaicin receptor TRPV1 ion channel is a polymodal nociceptor that responds to Heat with exquisite sensitivity through an unknown mechanism. Here we report the identification of a novel toxin, RhTx, from the venom of the Chinese red-headed centipede that potently activates TRPV1 to produce excruciating pain. RhTx is a 27-amino-acid small peptide that forms a compact polarized molecule with very rapid binding kinetics and high affinity for TRPV1. We show that RhTx targets the channel's Heat Activation machinery to cause powerful Heat Activation at body temperature. The RhTx-TRPV1 interaction is mediated by the toxin's highly charged C terminus, which associates tightly to the charge-rich outer pore region of the channel where it can directly interact with the pore helix and turret. These findings demonstrate that RhTx binding to the outer pore can induce TRPV1 Heat Activation, therefore providing crucial new structural information on the Heat Activation machinery.