A number of mutations have been described in the G protein Ras that have profound effects on its activity. For example, some mut

Question

21 day ago

14

A number of mutations have been described in the G protein Ras that have profound effects on its activity. For example, some mut

ations greatly increase the affinity of the G protein for GDP, making it very difficult for GDP to be exchanged for GTP. Other mutations prevent the GTPase activity of Ras, preventing it from causing the hydrolysis of GTP to GDP. Which of the scenarios would result in a persisting proliferation response to growth factor receptor activation after the ligand is no longer binding to its receptor kinase? a mutation that blocks the exchange of GDP with GTP a mutation that blocks the GTPase activity of Ras Both a mutation that blocks the GTPase activity of Ras and a mutation that blocks the exchange of GDP with GTP would cause the response to persist. Neither a mutation that blocks the GTPase activity of Ras nor a mutation that blocks the exchange of GDP with GTP would cause the response to persist.

Biology

1 answer:

enyata [2.5K] · Answer 1 · 2026-03-29T11:04:45+03:00

Answer:

a mutation that inhibits the GTPase function of Ras

Explanation:

A G protein is bound to GDP when inactive, and upon the action of a guanine exchange factor (GEF), it is substituted with GTP, leading to activation since GTP-bound state is considered active. This G protein possesses intrinsic GTPase activity, which is influenced by GAP. In the presence of GAP, the GTP hydrolyzes into GDP causing the G protein to become inactive. Consequently, a mutation blocking the GTPase activity of Ras leads to continuous active signaling even when there is no ligand binding to its receptor. In this scenario, GTP hydrolysis does not occur, resulting in upregulated signaling.