How do mutations in the KRAS gene affect its protein?

Mutations in the KRAS gene are known to play a significant role in many types of cancers by affecting the functionality of its protein products. The KRAS protein is a small GTPase that typically cycles between an active form (when bound to GTP) and an inactive form (when bound to GDP).

When mutations occur in the KRAS gene, they often lead to substitutions in amino acids that alter the protein's structure and function. Many of these mutations specifically prevent the KRAS protein from hydrolyzing GTP to GDP, which locks the protein in a constitutively active state. This means that the KRAS protein continuously sends pro-proliferative signals within the cell regardless of the presence of growth factors or other regulatory signals that would normally inactivate it. This unregulated signaling contributes to uncontrolled cell growth and the development of cancer.

Thus, the correct answer reflects this mechanism, indicating that mutations can lead to a situation where the KRAS protein is perpetually active, promoting ongoing cellular proliferation and survival, which are hallmarks of cancer.