Type of cytosolic enzyme that is activated by cAMP and functions to regulate the

Question

Type of cytosolic enzyme that is activated by cAMP and functions to regulate the activity of numerous cellular proteins. Generally is activated in response to a rise in cAMP level resulting from stimulation of G protein-coupled receptors. (3 words, sort of) A monomeric GTP-binding protein that functions in intracellular signaling pathways and is activated by ligand binding to receptor tyrosine kinases and other cell-surface receptors, (two words) A large family of heterodimeric transmembrane proteins that promote adhesion of cells to the extracellular matrix or to the surface of other cells. Conveying the message from outside the cell to the inside, often involves conformational changes in the receptor (two words)

Explanation / Answer

The PKA enzyme is also known as cAMP-dependent enzyme because it is activated only when cAMP is present. Hormones such as glucagon and epinephrine begin the activation cascade (that triggers protein kinase A) by binding to a G protein–coupled receptor (GPCR) on the target cell. When a GPCR is activated by its extracellular ligand, a conformational change is induced in the receptor that is transmitted to an attached intracellular heterotrimeric G protein complex by protein domain dynamics. The Gs alpha subunit of the stimulated G protein complex exchanges GDP for GTP and is released from the complex. The activated Gs alpha subunit binds to and activates an enzyme called adenylyl cyclase, which, in turn, catalyzes the conversion of ATP into cyclic adenosine monophosphate (cAMP) – increasing cAMP levels. Four cAMP molecules are required to activate a single PKA enzyme.

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