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Research shows that the high calcium selectivity of the cytosolic phospholipase A(sub)2 is influenced by cation charge and size and takes two metal ions to form a complex between the enzyme and the membrane. Structural aspects of the metal ion-binding site of the C2 domain of the enzyme are discussed.

The role of cytosolic phospholipase A2 (cPLA2 C2) domain in the Ca2+ ion binding was determined through utilization equilibrium binding and stopped-flow kinetic experiments. It was shown that Ca2+-regulated C2 domains typically bind two Ca2+ ions with positive cooperativity resulting in conformational change and membrane docking. Intrinsic fluorescence of Trp (super 71) was enhanced following binding of Ca2+ to the domain in the