V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog also known as KRAS is a protein which in humans is encoded by the KRAS gene. Like other members of the Ras family, the KRAS protein is a GTPase and is an early player in many signal transduction pathways. KRAS is usually tethered to cell membranes because of the presence of an isoprenyl group on its C-terminus.