Protein kinases are important in many aspects of cell signaling, cell maturation and differentiation, and metabolic control. Many of these enzymes are themselves regulated by phosphorylation, as well as by separate regulatory ligands. The effects of phosphorylation and ligand binding may also be synergistic. Many of these protein kinase activation signals are propagated in sequential protein phosphorylation steps, and the total activation can be very extensive for the final target enzyme. cAMP-dependent protein kinase provides an excellent example of how two ligands may each have a positive influence for the binding of the other one, even though the ligands bind to completely different subunits that are not in contact.
KeywordsProtein Kinase Adenylate Kinase Bovine Heart Positive Cooperativity cAMP Site
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