Physiology 3140A Chapter Notes -Hydrolysis, Eicosanoid, Diglyceride
4 Feb 2014
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Concentration of free mg2+ in cytoplasm is about 10-3 m thus ca2+ binding sites must have selectivity for. Ca2+ compared to mg2+ of at least 1000-fold. Receptors must have high affinity & selectivity. Calmodulin is an abundant ca2+ binding protein found in all eukaryotic cells which functions as a multi- purpose intracellular ca2+ receptor mediating many ca2+ related processes. Allosteric activation of calmodulin by ca2+ is analogous to allosteric activation of pka by camp but. Ca2+/calmodulin has no intrinsic enzyme activity itself but acts by binding to other proteins. In some cases, calmodulin is a permanent regulatory subunit of an enzyme. In most causes binding of ca2+ enables calmodulin to bind to various target proteins thereby altering their activity. Alternation of function of cellular proteins by ca2+ & calmodulin: Targets regulated by ca2+/calmodulin include various enzymes & membrane transporters. Most of the actions of ca2+ in the cell are mediated by ca2+/calmodulin-dependent proteins.
