Final answer:
The binding of Ran-GTP to an importin causes the disassociation of NLS-carrying proteins, allowing their entry into the nucleus. Inhibition of RAS G-protein GTPase activity leads to continuous activation of cell division pathways, contributing to cancer development.
Step-by-step explanation:
The binding of Ran-GTP to an importin, which is a type of nuclear import receptor, typically results in the disassociation of nuclear localization signals (NLS)-carrying proteins from the importin. This allows for subsequent transport into the cell nucleus. The importin-Ran-GTP complex is then recognized by the nuclear pore complex and is transported into the nucleus. Once inside, Ran-GTP is hydrolyzed to Ran-GDP which leads to the release of the importin, completing the cycle of nuclear import.
In the context of RAS G-protein and cancer, the inhibition of GTPase activity means RAS cannot convert GTP to GDP. This retained GTP-bound state of RAS results in the continuous activation of downstream signaling pathways that promote cell division. Consequently, cells proliferate uncontrollably, which is a hallmark of cancer. Thus, targeting this pathway with drugs that inhibit the GTP-bound RAS could potentially be a strategy for cancer treatment.