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Photo Lynn Kamerlin

Lynn Kamerlin

Professor

Photo Lynn Kamerlin

GTP Hydrolysis Without an Active Site Base : A Unifying Mechanism for Ras and Related GTPases

Author

  • Ana R Calixto
  • Cátia Moreira
  • Anna Pabis
  • Carsten Kötting
  • Klaus Gerwert
  • Till Rudack
  • Shina C L Kamerlin

Summary, in English

GTP hydrolysis is a biologically crucial reaction, being involved in regulating almost all cellular processes. As a result, the enzymes that catalyze this reaction are among the most important drug targets. Despite their vital importance and decades of substantial research effort, the fundamental mechanism of enzyme-catalyzed GTP hydrolysis by GTPases remains highly controversial. Specifically, how do these regulatory proteins hydrolyze GTP without an obvious general base in the active site to activate the water molecule for nucleophilic attack? To answer this question, we perform empirical valence bond simulations of GTPase-catalyzed GTP hydrolysis, comparing solvent- and substrate-assisted pathways in three distinct GTPases, Ras, Rab, and the Gαi subunit of a heterotrimeric G-protein, both in the presence and in the absence of the corresponding GTPase activating proteins. Our results demonstrate that a general base is not needed in the active site, as the preferred mechanism for GTP hydrolysis is a conserved solvent-assisted pathway. This pathway involves the rate-limiting nucleophilic attack of a water molecule, leading to a short-lived intermediate that tautomerizes to form H2PO4- and GDP as the final products. Our fundamental biochemical insight into the enzymatic regulation of GTP hydrolysis not only resolves a decades-old mechanistic controversy but also has high relevance for drug discovery efforts. That is, revisiting the role of oncogenic mutants with respect to our mechanistic findings would pave the way for a new starting point to discover drugs for (so far) "undruggable" GTPases like Ras.

Publishing year

2019-07-10

Language

English

Pages

10684-10701

Publication/Series

Journal of the American Chemical Society

Volume

141

Issue

27

Document type

Journal article

Publisher

The American Chemical Society (ACS)

Keywords

  • Animals
  • Catalytic Domain
  • Enzyme Activation
  • GTP Phosphohydrolases/chemistry
  • Guanosine Triphosphate/metabolism
  • Humans
  • Hydrolysis
  • Models, Molecular

Status

Published

ISBN/ISSN/Other

  • ISSN: 1520-5126