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Reconstituted IMPDH polymers accommodate both catalytically active and inactive conformations

Several metabolic enzymes undergo reversible polymerization into macromolecular assemblies. The function of these assemblies is often unclear, but in some cases they regulate enzyme activity and metabolic homeostasis. The guanine nucleotide biosynthetic enzyme inosine monophosphate dehydrogenase (IM...

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Autores principales: Anthony, Sajitha A., Burrell, Anika L., Johnson, Matthew C., Duong-Ly, Krisna C., Kuo, Yin-Ming, Simonet, Jacqueline C., Michener, Peter, Andrews, Andrew, Kollman, Justin M., Peterson, Jeffrey R.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The American Society for Cell Biology 2017
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5620369/
https://www.ncbi.nlm.nih.gov/pubmed/28794265
http://dx.doi.org/10.1091/mbc.E17-04-0263
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author Anthony, Sajitha A.
Burrell, Anika L.
Johnson, Matthew C.
Duong-Ly, Krisna C.
Kuo, Yin-Ming
Simonet, Jacqueline C.
Michener, Peter
Andrews, Andrew
Kollman, Justin M.
Peterson, Jeffrey R.
author_facet Anthony, Sajitha A.
Burrell, Anika L.
Johnson, Matthew C.
Duong-Ly, Krisna C.
Kuo, Yin-Ming
Simonet, Jacqueline C.
Michener, Peter
Andrews, Andrew
Kollman, Justin M.
Peterson, Jeffrey R.
author_sort Anthony, Sajitha A.
collection PubMed
description Several metabolic enzymes undergo reversible polymerization into macromolecular assemblies. The function of these assemblies is often unclear, but in some cases they regulate enzyme activity and metabolic homeostasis. The guanine nucleotide biosynthetic enzyme inosine monophosphate dehydrogenase (IMPDH) forms octamers that polymerize into helical chains. In mammalian cells, IMPDH filaments can associate into micron-length assemblies. Polymerization and enzyme activity are regulated in part by binding of purine nucleotides to an allosteric regulatory domain. ATP promotes octamer polymerization, whereas guanosine triphosphate (GTP) promotes a compact, inactive conformation whose ability to polymerize is unknown. Also unclear is whether polymerization directly alters IMPDH catalytic activity. To address this, we identified point mutants of human IMPDH2 that either prevent or promote polymerization. Unexpectedly, we found that polymerized and nonassembled forms of recombinant IMPDH have comparable catalytic activity, substrate affinity, and GTP sensitivity and validated this finding in cells. Electron microscopy revealed that substrates and allosteric nucleotides shift the equilibrium between active and inactive conformations in both the octamer and the filament. Unlike other metabolic filaments, which selectively stabilize active or inactive conformations, recombinant IMPDH filaments accommodate multiple states. These conformational states are finely tuned by substrate availability and purine balance, while polymerization may allow cooperative transitions between states.
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spelling pubmed-56203692017-12-16 Reconstituted IMPDH polymers accommodate both catalytically active and inactive conformations Anthony, Sajitha A. Burrell, Anika L. Johnson, Matthew C. Duong-Ly, Krisna C. Kuo, Yin-Ming Simonet, Jacqueline C. Michener, Peter Andrews, Andrew Kollman, Justin M. Peterson, Jeffrey R. Mol Biol Cell Brief Reports Several metabolic enzymes undergo reversible polymerization into macromolecular assemblies. The function of these assemblies is often unclear, but in some cases they regulate enzyme activity and metabolic homeostasis. The guanine nucleotide biosynthetic enzyme inosine monophosphate dehydrogenase (IMPDH) forms octamers that polymerize into helical chains. In mammalian cells, IMPDH filaments can associate into micron-length assemblies. Polymerization and enzyme activity are regulated in part by binding of purine nucleotides to an allosteric regulatory domain. ATP promotes octamer polymerization, whereas guanosine triphosphate (GTP) promotes a compact, inactive conformation whose ability to polymerize is unknown. Also unclear is whether polymerization directly alters IMPDH catalytic activity. To address this, we identified point mutants of human IMPDH2 that either prevent or promote polymerization. Unexpectedly, we found that polymerized and nonassembled forms of recombinant IMPDH have comparable catalytic activity, substrate affinity, and GTP sensitivity and validated this finding in cells. Electron microscopy revealed that substrates and allosteric nucleotides shift the equilibrium between active and inactive conformations in both the octamer and the filament. Unlike other metabolic filaments, which selectively stabilize active or inactive conformations, recombinant IMPDH filaments accommodate multiple states. These conformational states are finely tuned by substrate availability and purine balance, while polymerization may allow cooperative transitions between states. The American Society for Cell Biology 2017-10-01 /pmc/articles/PMC5620369/ /pubmed/28794265 http://dx.doi.org/10.1091/mbc.E17-04-0263 Text en © 2017 Anthony et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0). “ASCB®,” “The American Society for Cell Biology®,” and “Molecular Biology of the Cell®” are registered trademarks of The American Society for Cell Biology.
spellingShingle Brief Reports
Anthony, Sajitha A.
Burrell, Anika L.
Johnson, Matthew C.
Duong-Ly, Krisna C.
Kuo, Yin-Ming
Simonet, Jacqueline C.
Michener, Peter
Andrews, Andrew
Kollman, Justin M.
Peterson, Jeffrey R.
Reconstituted IMPDH polymers accommodate both catalytically active and inactive conformations
title Reconstituted IMPDH polymers accommodate both catalytically active and inactive conformations
title_full Reconstituted IMPDH polymers accommodate both catalytically active and inactive conformations
title_fullStr Reconstituted IMPDH polymers accommodate both catalytically active and inactive conformations
title_full_unstemmed Reconstituted IMPDH polymers accommodate both catalytically active and inactive conformations
title_short Reconstituted IMPDH polymers accommodate both catalytically active and inactive conformations
title_sort reconstituted impdh polymers accommodate both catalytically active and inactive conformations
topic Brief Reports
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5620369/
https://www.ncbi.nlm.nih.gov/pubmed/28794265
http://dx.doi.org/10.1091/mbc.E17-04-0263
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