Question

Briefly describe the experimental approach you would use to test the hypothesis that active Cdc42, but not inactive Cdc42, can bind and recruit WASP to the plasma membrane of cells.

Answer 1

Cdc 42 is a molecular switch like other rho proteins. These are active in GTP form and inactive at GDP form. Mutation experiments are mainly employed for the study of these molecular switches. So scientists introduce mutant proteins into the cells. That will lock the Cdc in either inactive or active state. Then we can study the outcome of the cascade with both active form and inactive form. And one can introduce a dominant mutant which binds and inhibit GEF. so the Cdcs will be sequester at inactive GDP form because GEF is essential for the conversion of inactive GDP form to active GTP form. So If we block the activity of  GEF all the Cdc will be sequestered in an inactive form and prevent recruitment of the WASP so the further signaling cascade will cease.

Actually the Cdc will recruit WASP and it will recruit Arp2/3 and leads to actin polymerization. So if the Cdc 42 is in inactive GDP form, it cant recruit WASP and it blocks further cascade and there is no outcome.

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