Answer to Question #95278 in Biochemistry for Yunzila Iftikhar

Question

All of the following are true about hetrotrimeric g protein except

a) they bind either gdp or gtp
b) they have gtpase activity
c) they act as binary(on/off) switches
d) they help amplify hormones signal
e) they phosphorylate proteins
please answer this query..thank you..

Answer 1

e. they phosphorylate proteins -this is not true.

G proteins are specialized proteins with the ability to bind the nucleotides guanosine triphosphate (GTP) and guanosine diphosphate (GDP). A G protein alpha subunit binds either GTP or GDP depending on whether the protein is active (GTP) or inactive (GDP).

 G proteins work like a switch — turned on or off by signal-receptor interactions on the cell's surface.

 A G proteins are controlled by GEFs which catalyse the sequential release and binding of guanine nucleotides, and by GTPase activity.

G proteins help amplify hormones signal.

G proteins act as second messenger and thus they amplify hormone signals.

they do not phosphorylate proteins. This work is performed by the kinase present in the cell.