Structural basis of the atypical activation mechanism of KRASV14I

Asim K. Bera, Jia Lu, Thomas E. Wales, Sudershan Gondi, Deepak Gurbani, Andrew Nelson, John R. Engen, Kenneth D. Westover

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

RAS regulation and signaling are largely accomplished by direct protein-protein interactions, making RAS protein dynamics a critical determinant of RAS function. Here, we report a crystal structure of GDP-bound KRASV14I, a mutated KRAS variant associated with the developmental RASopathy disorder Noonan syndrome (NS), at 1.5-1.6 Å resolution. The structure is notable for revealing a marked extension of switch 1 away from the G-domain and nucleotide-binding site of the KRAS protein. We found that this extension is associated with a loss of the magnesium ion and a tilt in the position of the guanine base because of the additional carbon introduced by the isoleucine substitution. Hydrogen-deuterium exchange MS analysis confirmed that this conformation occurs in solution, but also disclosed a difference in kinetics when compared with KRASA146T, another RAS mutant that displays a nearly identical conformation in previously reported crystal structures. This conformational change contributed to a high rate of guanine nucleotide-exchange factor (GEF)-dependent and -independent nucleotide exchange and to an increase in affinity for SOS Ras/Rac GEF 1 (SOS1), which appears to be the major mode of activation for this RAS variant. These results highlight a mechanistic connection between KRASA146T and KRASV14I that may have implications for the regulation of these variants and for the development of therapeutic strategies to manage KRAS variantassociated disorders.

Original languageEnglish (US)
Pages (from-to)13964-13972
Number of pages9
JournalJournal of Biological Chemistry
Volume294
Issue number38
DOIs
StatePublished - Sep 20 2019

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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