K-Ras PI3K complex. Computer model showing the structure of a molecule of the K-Ras oncogene protein (white, right) in complex with GTP (spheres, bottom left), benzamidine (spheres, upper centre) and four domains of the PI3K (phosphoinositide 3-kinase) gamma subunit. RBD (green), C2 domain (pale green), helical domain (purple), and N- and C-terminal lobes of the catalytic domain (red and yellow) are shown. The location of the g phosphate of the ATP PI3K gamma structure is marked with a large phosphate molecule (orange and red spheres). Ras proteins are involved in transmitting signals within cells. They are GTPase enzymes - they bind and hydrolyze GTP. Mutations in the K-Ras gene is an essential step in the development of many cancers, therefore this protein is classed as an oncogene protein. Ras inhibitors such as benzamidine are being studied as a treatment for cancer.