The Experts below are selected from a list of 5421 Experts worldwide ranked by ideXlab platform
Giuseppe D Tocchinivalentini - One of the best experts on this subject based on the ideXlab platform.
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structure function and evolution of the trna endonucleases of archaea an example of subfunctionalization
Proceedings of the National Academy of Sciences of the United States of America, 2005Co-Authors: Paolo Fruscoloni, Giuseppe D TocchinivalentiniAbstract:We have detected two paralogs of the tRNA endonuclease gene of Methanocaldococcus jannaschii in the genome of the crenarchaeote Sulfolobus solfataricus. This finding has led to the discovery of a previously unrecognized oligomeric form of the enzyme. The two genes code for two different subunits, both of which are required for cleavage of the pre-tRNA substrate. Thus, there are now three forms of tRNA endonuclease in the Archaea: a Homotetramer in some Euryarchaea, a homodimer in other Euryarchaea, and a heterotetramer in the Crenarchaea and the Nanoarchaea. The last-named enzyme, arising most likely by gene duplication and subsequent “subfunctionalization,” requires the products of both genes to be active.
Richard Béliveau - One of the best experts on this subject based on the ideXlab platform.
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the renal brush border membrane sodium sulfate cotransporter functions in situ as a Homotetramer
The International Journal of Biochemistry & Cell Biology, 1996Co-Authors: Marc Jetté, Julie Pelletier, Michel Potier, Richard BéliveauAbstract:Abstract The functional molecular size of the renal Na + SO 4 2− cotransporter was analysed with the radiation inactivation and fragmentation method. Purified brush border membrane vesicles preserved in a cryoprotective medium were exposed to γ-radiations. Initial rates of SO42− influx into these vesicles were estimated with membranes irradiated with 0, 4 and 8 Mrad. In each case, SO42− uptake by irradiated membranes was significantly reduced but remained linear during the first 5 sec of incubation. To avoid artifacts arising from a decrease in the driving force caused by modifications in membrane permeability, this incubation period was chosen to measure the effect of irradiation on the SO42− transport activity. Increasing irradiation doses resulted in a monoexponential decrease in transport activity allowing the molecular size to be estimated at 238 ± 6 kDa (SD, n = 3). Recently, a cDNA for the Na + /SO42− cotransporter was cloned and expressed in Xenopus laevis oocytes (Markovich D. et al. (1993) Proc. Natl Acad. Sci. U.S.A. 90, 8073–8077). The deduced amino acid sequence of this cotransporter predicts a molecular weight of 66 kDa. We suggest that the in situ activity of the renal brush border membrane Na + SO 4 2− cotransporter requires the presence of four intact and identical subunits arranged as a Homotetramer.
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The renal brush border membrane sodium/sulfate cotransporter functions in situ as a Homotetramer
The International Journal of Biochemistry & Cell Biology, 1996Co-Authors: Marc Jetté, Julie Pelletier, Michel Potier, Richard BéliveauAbstract:Abstract The functional molecular size of the renal Na + SO 4 2− cotransporter was analysed with the radiation inactivation and fragmentation method. Purified brush border membrane vesicles preserved in a cryoprotective medium were exposed to γ-radiations. Initial rates of SO42− influx into these vesicles were estimated with membranes irradiated with 0, 4 and 8 Mrad. In each case, SO42− uptake by irradiated membranes was significantly reduced but remained linear during the first 5 sec of incubation. To avoid artifacts arising from a decrease in the driving force caused by modifications in membrane permeability, this incubation period was chosen to measure the effect of irradiation on the SO42− transport activity. Increasing irradiation doses resulted in a monoexponential decrease in transport activity allowing the molecular size to be estimated at 238 ± 6 kDa (SD, n = 3). Recently, a cDNA for the Na + /SO42− cotransporter was cloned and expressed in Xenopus laevis oocytes (Markovich D. et al. (1993) Proc. Natl Acad. Sci. U.S.A. 90, 8073–8077). The deduced amino acid sequence of this cotransporter predicts a molecular weight of 66 kDa. We suggest that the in situ activity of the renal brush border membrane Na + SO 4 2− cotransporter requires the presence of four intact and identical subunits arranged as a Homotetramer.
Marc Jetté - One of the best experts on this subject based on the ideXlab platform.
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the renal brush border membrane sodium sulfate cotransporter functions in situ as a Homotetramer
The International Journal of Biochemistry & Cell Biology, 1996Co-Authors: Marc Jetté, Julie Pelletier, Michel Potier, Richard BéliveauAbstract:Abstract The functional molecular size of the renal Na + SO 4 2− cotransporter was analysed with the radiation inactivation and fragmentation method. Purified brush border membrane vesicles preserved in a cryoprotective medium were exposed to γ-radiations. Initial rates of SO42− influx into these vesicles were estimated with membranes irradiated with 0, 4 and 8 Mrad. In each case, SO42− uptake by irradiated membranes was significantly reduced but remained linear during the first 5 sec of incubation. To avoid artifacts arising from a decrease in the driving force caused by modifications in membrane permeability, this incubation period was chosen to measure the effect of irradiation on the SO42− transport activity. Increasing irradiation doses resulted in a monoexponential decrease in transport activity allowing the molecular size to be estimated at 238 ± 6 kDa (SD, n = 3). Recently, a cDNA for the Na + /SO42− cotransporter was cloned and expressed in Xenopus laevis oocytes (Markovich D. et al. (1993) Proc. Natl Acad. Sci. U.S.A. 90, 8073–8077). The deduced amino acid sequence of this cotransporter predicts a molecular weight of 66 kDa. We suggest that the in situ activity of the renal brush border membrane Na + SO 4 2− cotransporter requires the presence of four intact and identical subunits arranged as a Homotetramer.
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The renal brush border membrane sodium/sulfate cotransporter functions in situ as a Homotetramer
The International Journal of Biochemistry & Cell Biology, 1996Co-Authors: Marc Jetté, Julie Pelletier, Michel Potier, Richard BéliveauAbstract:Abstract The functional molecular size of the renal Na + SO 4 2− cotransporter was analysed with the radiation inactivation and fragmentation method. Purified brush border membrane vesicles preserved in a cryoprotective medium were exposed to γ-radiations. Initial rates of SO42− influx into these vesicles were estimated with membranes irradiated with 0, 4 and 8 Mrad. In each case, SO42− uptake by irradiated membranes was significantly reduced but remained linear during the first 5 sec of incubation. To avoid artifacts arising from a decrease in the driving force caused by modifications in membrane permeability, this incubation period was chosen to measure the effect of irradiation on the SO42− transport activity. Increasing irradiation doses resulted in a monoexponential decrease in transport activity allowing the molecular size to be estimated at 238 ± 6 kDa (SD, n = 3). Recently, a cDNA for the Na + /SO42− cotransporter was cloned and expressed in Xenopus laevis oocytes (Markovich D. et al. (1993) Proc. Natl Acad. Sci. U.S.A. 90, 8073–8077). The deduced amino acid sequence of this cotransporter predicts a molecular weight of 66 kDa. We suggest that the in situ activity of the renal brush border membrane Na + SO 4 2− cotransporter requires the presence of four intact and identical subunits arranged as a Homotetramer.
Jianren Lu - One of the best experts on this subject based on the ideXlab platform.
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purification and characterization of a hyperthermostable mn superoxide dismutase from thermus thermophilus hb27
Extremophiles, 2011Co-Authors: Jianren LuAbstract:Thermostable Mn-dependent catalases are promising enzymes in biotechnological applications. In the present study, a Mn-containing superoxide dismutase of the hyperthermophilic Thermus thermophilus HB27 had been purified and characterized by a two-stage ultrafiltration process after being expressed in E. coli. The enzyme was highly stable at 90°C and retained 57% activity after heat treatment at 100°C for 1 h. The native form of the enzyme was determined as a Homotetramer by analytical size exclusion chromatography and sodium dodecyl sulfate–polyacrylamide gel electrophoresis. The final purified enzyme had an isoelectric point of 6.2 and a high α-helical content of 70%, consistent with the theoretical values. This showed that the purified SOD folded with a reasonable secondary structure.
Michael J Edwardson - One of the best experts on this subject based on the ideXlab platform.
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atomic force microscopy reveals the alternating subunit arrangement of the trpp2 trpv4 heterotetramer
Biophysical Journal, 2010Co-Authors: Andrew P Stewart, Graham D Smith, Richard Sandford, Michael J EdwardsonAbstract:There is evidence that polycystin-2 (TRPP2) interacts with two other members of the transient receptor potential (TRP) family, TRPC1 and TRPV4. We have previously shown that TRPP2 forms a heteromeric complex with TRPC1, with a 2:2 stoichiometry and an alternating subunit arrangement. Here, we used coimmunoprecipitation to show that TRPP2 also interacts with TRPV4, but not with TRPA1 or TRPM8; hence, its promiscuity is limited. We then used atomic force microscopy to study the structure of the TRPV4 homomer and the interaction between TRPP2 and TRPV4. The molecular volume of V5-tagged TRPV4 isolated from singly-transfected tsA 201 cells indicated that it assembled as a Homotetramer. The distribution of angles between pairs of anti-V5 antibodies bound to TRPV4 particles had a large peak close to 90° and a smaller peak close to 180°, again consistent with the assembly of TRPV4 as a Homotetramer. In contrast, the angle distributions for decoration of the TRPP2-TRPV4 heteromer by either anti-Myc or anti-V5 antibodies had major peaks close to 180°. This result indicates that TRPP2-TRPV4 assembles identically to TRPP2-TRPC1, suggesting a common subunit arrangement among heteromeric TRP channels.
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the transient receptor potential channels trpp2 and trpc1 form a heterotetramer with a 2 2 stoichiometry and an alternating subunit arrangement
Journal of Biological Chemistry, 2009Co-Authors: Toshiro Kobori, Richard Sandford, Graham D Smith, Michael J EdwardsonAbstract:There is functional evidence that polycystin-2 (TRPP2) interacts with other members of the transient receptor potential family, including TRPC1 and TRPV4. Here we have used atomic force microscopy to study the structure of the TRPP2 homomer and the interaction between TRPP2 and TRPC1. The molecular volumes of both Myc-tagged TRPP2 and V5-tagged TRPC1 isolated from singly transfected tsA 201 cells indicated that they assembled as Homotetramers. The molecular volume of the protein isolated from cells expressing both TRPP2 and TRPC1 was intermediate between the volumes of the two homomers, suggesting that a heteromer was being formed. The distribution of angles between pairs of anti-Myc antibodies bound to TRPP2 particles had a large peak close to 90° and a smaller peak close to 180°, consistent with the assembly of TRPP2 as a Homotetramer. In contrast, the corresponding angle distributions for decoration of the TRPP2-TRPC1 heteromer by either anti-Myc or anti-V5 antibodies had predominant peaks close to 180°. This decoration pattern indicates a TRPP2:TRPC1 subunit stoichiometry of 2:2 and an alternating subunit arrangement.