Characterization of the plant nicotinamide adenine dinucleotide kinase activator protein and its identification as calmodulin

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Abstract
A protein activator of plant NAD kinase was extracted from plant sources (peanuts [Arachis hypogaea] and peas [Pisum sativum]), purified to homogeneity, characterized, and identified as calmodulin. A comparison of the properties of calmodulin isolated from either plant or animal [a coelenterate, Renilla reniformis] sources shows that they are strikingly similar proteins. The similarities include molecular weight, Stokes radii, amino acid composition, Ca2+-dependent enhancement of tyrosine fluorescence, Ca2+-dependent interaction with troponin I, equal abilities to activate cyclic nucleotide phosphodiesterase, Ca2+-dependent inhibition of calmodulin action by the phenothiazine drugs, and electrophoretic mobility. Plant cells may undergo Ca2+-dependent regulatory events that are mediated by calmodulin in a manner similar to those found in animals.