Answer to Pharmacology MCQ 455

The Correct option is A

It has been known for some time that hetero-trimeric G proteins are found not only at the plasma membrane but also on intracellular membranes. G proteins act as molecular switches by interacting with and regulating other proteins, often enzymes, in response to specific stimuli. G proteins are critical to the regulation of many processes in eukaryotic cells, including translation and trafficking of proteins into the nucleus.G proteins get their name from Guanine nucleotide binding protein, and the binding of specific quinine nucleotides dictates whether the protein is “on” or “off”.

Two broad classes of G proteins are seen: heterotrimeric and monomeric. As these names suggest, these differ in their polypeptide subunit composition. The heterotrimeric G proteins consist of three subunits (designated alpha, beta, and gamma), while the monomeric G proteins (sometimes called the small GTPases) consist of only a single polypeptide. These two classes generally differ in the signal transduction pathways they activate. The hetertrimeric G proteins typically regulate second messenger systems (i.e., adenylate cyclase, guanylate cyclase, phospholipase C), while the monomeric G proteins typically regulate kinase cascade systems (i.e., those activated in response to growth factor stimulation).

Category: Pharmacology MCQs