KRAS
KRAS is a small GTP-binding protein that relays signals from growth-factor receptors to the kinase cascades that drive proliferation. It is among the most frequently activated oncogenes in human cancer.
Function
KRAS is bound to the inner face of the plasma membrane. A growth-factor receptor such as EGFR activates it by catalyzing GDP-to-GTP exchange; KRAS-GTP then recruits and activates RAF, starting the MAPK cascade toward MEK and ERK, alongside PI3K and other effectors. KRAS hydrolyzes its own bound GTP to switch off; GAP proteins accelerate this hydrolysis, and growth-factor receptors activate KRAS by promoting GDP-to-GTP exchange.
In cancer
Point mutations at codons 12, 13, and 61 destroy the GTPase activity,
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