Final answer:
GEF enhances GTPase activity by promoting GTP binding. When RAS G-protein's GTPase activity is inhibited, it causes unregulated cell growth, characteristic of cancer. This uncontrolled signaling can promote cancer progression.
Step-by-step explanation:
The guanine nucleotide exchange factor (GEF) regulates small GTPase activity by facilitating the exchange of guanosine diphosphate (GDP) for guanosine triphosphate (GTP) on the GTPase. In the context of cancer, if the GTPase activity of the RAS G-protein is inhibited, it cannot hydrolyze GTP into GDP, leading to constitutive activation of the RAS protein. As a result, the downstream cellular events that are normally tightly controlled by RAS, such as cell growth and division, are no longer regulated. This unregulated signaling can result in uncontrolled cell growth, a characteristic feature of cancer. Cell signaling involving G-protein-coupled receptors is crucial for managing cell functions, and when these pathways malfunction, such as in the case of the RAS G-protein no longer being able to switch off, it may lead to the progression of cancer.