Signal Transduction Through Receptors that Reside in the Plasma Membrane

Tyrosine-kinase-dependent receptors generally signal to the nucleus and regulate gene transcription through multiple pathways. One way that these receptors communicate with the genome is through activation of the mitogen-activated protein (MAP) kinase cascade (Fig. 18). MAP kinase is a cytosolic enzyme that is activated by phosphorylation of both serine and tyro-sine residues and then enters the nucleus, where it phosphorylates and activates certain transcription factors. Activation of MAP kinase follows an indirect route that involves a small G-protein, called Ras, which was originally discovered as a constitutively activated protein present in many tumors. Ras proteins belong to a family of small G-proteins that function as biochemical switches to regulate such processes as entry of proteins into the nucleus, sorting and trafficking of intracellular vesicles, and cytoskeletal rearrangements. The small G-proteins are members of the same super-family as the a subunit of the heterotrimeric G-proteins but do not form complexes with Py subunits or interact directly with receptors. The small G-proteins are GTPases that are in their active state when bound to GTP and in their inactive state when bound to GDP. Instead of liganded receptors, the small G-proteins are activated by proteins called nucleotide exchange factors that cause them to dissociate from GDP and bind GTP.

Get Rid of Gallstones Naturally

Get Rid of Gallstones Naturally

One of the main home remedies that you need to follow to prevent gallstones is a healthy lifestyle. You need to maintain a healthy body weight to prevent gallstones. The following are the best home remedies that will help you to treat and prevent gallstones.

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