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Title: Neutron crystal structure of RAS GTPase puts in question the protonation state of the GTP γ-phosphate

RAS GTPase is a prototype for nucleotide-binding proteins that function by cycling between GTP and GDP, with hydrogen atoms playing an important role in the GTP hydrolysis mechanism. It is one of the most well studied proteins in the superfamily of small GTPases, which has representatives in a wide range of cellular functions. These proteins share a GTP-binding pocket with highly conserved motifs that promote hydrolysis to GDP. The neutron crystal structure of RAS presented here strongly supports a protonated gamma-phosphate at physiological pH. This counters the notion that the phosphate groups of GTP are fully deprotonated at the start of the hydrolysis reaction, which has colored the interpretation of experimental and computational data in studies of the hydrolysis mechanism. As a result, the neutron crystal structure presented here puts in question our understanding of the pre-catalytic state associated with the hydrolysis reaction central to the function of RAS and other GTPases.
 [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Northeastern Univ., Boston, MA (United States)
  2. North Carolina State Univ., Raleigh, NC (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. North Carolina State Univ., Raleigh, NC (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  5. Northeastern Univ., Boston, MA (United States); North Carolina State Univ., Raleigh, NC (United States)
Publication Date:
OSTI Identifier:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of Biological Chemistry
Additional Journal Information:
Journal Volume: 290; Journal Issue: 52; Journal ID: ISSN 0021-9258
American Society for Biochemistry and Molecular Biology
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). High Flux Isotope Reactor (HFIR); Center for Structural Molecular Biology (CSMB)
Sponsoring Org:
Country of Publication:
United States
59 BASIC BIOLOGICAL SCIENCES enzyme catalysls; neutron diffraction; Ras protein; small GTPase; structural biology