Question

How would having a loss of function of RanGAP impact the trafficking of nuclear proteins?

Answer 1

Ran (RAs-related Nuclear protein) also known as GTP-binding nuclear protein Ran is a protein that in humans is encoded by the RAN gene. Ran is a small 25 kDa protein that is involved in transport into and out of the cell nucleus during interphase and also involved in mitosis. It is a member of the Ras superfamily

Ran is a small G protein that is essential for the translocation of RNA and proteins through the nuclear pore complex. The Ran protein has also been implicated in the control of DNA synthesis and cell cycle progression, as mutations in Ran have been found to disrupt DNA synthesis.

In model species such as the yeast Saccharomyces cerevisiae, the primate Homo sapiens (See RANGAP1) and the plant Arabidopsis thaliana, it acts as a GTPase-activating protein, catalysing the conversion of cytosolically-bound RanGTP to RanGDP. It has the opposite function of the RCC1, a nuclear-located protein that converts RanGDP to RanGTP. Together, RanGAP and RCC1 maintain what is known as the ran gradient, where RanGDP is in higher concentrations in the cytosol, while RanGTP is in higher concentrations in the nucleus. It is this ran gradient which provides the energy necessary for the transport of proteins into and out of the nucleus by karyopherin proteins

That is why loss of function of ranGAP blocks the trafficking of nuclear proteins.

Hope it will help you understand the concept.