Dissecting the thermodynamics of GAP-RhoA interactions

J Struct Biol. 2009 Jan;165(1):10-8. doi: 10.1016/j.jsb.2008.09.007. Epub 2008 Oct 2.


We describe a detailed study of the RhoA-binding epitope of the GAP domain of Graf, including the determination of the thermodynamic and kinetic parameters of the interaction of wild-type domain, and of its 15 single-site mutants, with cognate GTPases. We show that residues important for the structural integrity of the Arg-finger loop are critical for binding Rho and for the catalytic activity of GAP, but GTPase selectivity appears to be modulated by a much more subtle interplay of electrostatic and hydrophobic interactions involving residues on the periphery of the main interface. The eight residues targeted in this study are involved in three distinct patches on the surface, two of which appear to interact with highly conserved regions of the GTPase, while the third plays a role in GTPase selectivity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • GTPase-Activating Proteins / chemistry*
  • GTPase-Activating Proteins / genetics
  • GTPase-Activating Proteins / metabolism*
  • Guanosine Triphosphate / metabolism
  • Humans
  • Molecular Sequence Data
  • Sequence Alignment
  • Thermodynamics
  • rhoA GTP-Binding Protein / chemistry*
  • rhoA GTP-Binding Protein / genetics
  • rhoA GTP-Binding Protein / metabolism*


  • ARHGAP26 protein, human
  • GTPase-Activating Proteins
  • RHOA protein, human
  • Guanosine Triphosphate
  • rhoA GTP-Binding Protein