Small-molecule ligands bind to a distinct pocket in Ras and inhibit SOS-mediated nucleotide exchange activity

Proc Natl Acad Sci U S A. 2012 Apr 3;109(14):5299-304. doi: 10.1073/pnas.1116510109. Epub 2012 Mar 19.


The Ras gene is frequently mutated in cancer, and mutant Ras drives tumorigenesis. Although Ras is a central oncogene, small molecules that bind to Ras in a well-defined manner and exert inhibitory effects have not been uncovered to date. Through an NMR-based fragment screen, we identified a group of small molecules that all bind to a common site on Ras. High-resolution cocrystal structures delineated a unique ligand-binding pocket on the Ras protein that is adjacent to the switch I/II regions and can be expanded upon compound binding. Structure analysis predicts that compound-binding interferes with the Ras/SOS interactions. Indeed, selected compounds inhibit SOS-mediated nucleotide exchange and prevent Ras activation by blocking the formation of intermediates of the exchange reaction. The discovery of a small-molecule binding pocket on Ras with functional significance provides a new direction in the search of therapeutically effective inhibitors of the Ras oncoprotein.

MeSH terms

  • Binding Sites
  • Cell Line
  • Humans
  • Ligands
  • Models, Molecular
  • Nuclear Magnetic Resonance, Biomolecular
  • Nucleotides / metabolism*
  • Son of Sevenless Proteins / metabolism*
  • ras Proteins / chemistry
  • ras Proteins / metabolism*


  • Ligands
  • Nucleotides
  • Son of Sevenless Proteins
  • ras Proteins

Associated data

  • PDB/4DSO
  • PDB/4DST
  • PDB/4DSU