Isoform-Specific Destabilization of the Active Site Reveals a Molecular Mechanism of Intrinsic Activation of KRas G13D

Cell Rep. 2019 Aug 6;28(6):1538-1550.e7. doi: 10.1016/j.celrep.2019.07.026.

Abstract

Ras GTPases are mutated at codons 12, 13, and 61, with different frequencies in KRas, HRas, and NRas and in a cancer-specific manner. The G13D mutant appears in 25% of KRas-driven colorectal cancers, while observed only rarely in HRas or NRas. Structures of Ras G13D in the three isoforms show an open active site, with adjustments to the D13 backbone torsion angles and with disconnected switch regions. KRas G13D has unique features that destabilize the nucleotide-binding pocket. In KRas G13D bound to GDP, A59 is placed in the Mg2+ binding site, as in the HRas-SOS complex. Structure and biochemistry are consistent with an intermediate level of KRas G13D bound to GTP, relative to wild-type and KRas G12D, observed in genetically engineered mouse models. The results explain in part the elevated frequency of the G13D mutant in KRas over the other isoforms of Ras.

Keywords: KRas G12D; KRas G13D mouse model; KRas G13D structures; Ras GTPases; Ras conformational states; activation cycle; colorectal cancer; nucleotide exchange mutant; oncogene.

Publication types

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

MeSH terms

  • Animals
  • Catalytic Domain
  • Cell Line, Tumor
  • Colon / metabolism
  • Female
  • Homeostasis
  • Humans
  • Hydrolysis
  • Intestinal Mucosa / metabolism
  • Male
  • Mice
  • Models, Molecular
  • Mutation*
  • Protein Conformation
  • Protein Isoforms / chemistry
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Protein Stability
  • Proto-Oncogene Proteins p21(ras) / chemistry
  • Proto-Oncogene Proteins p21(ras) / genetics
  • Proto-Oncogene Proteins p21(ras) / metabolism*
  • Structure-Activity Relationship

Substances

  • Protein Isoforms
  • Proto-Oncogene Proteins p21(ras)