Comparison of calcium-modulated proteins from vertebrate brains

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Abstract
Calmodulins have been purified from porcine, rabbit, rat, and chicken brains and their structural and functional properties compared to those of the bovine brain protein whose complete amino acid sequence has been elucidated. No major differences were detected in the amino acid compositions and tryptic peptide maps of these 5 proteins. All calmodulins lacked tryptophan and cysteine and contained 1 mol of N.epsilon.-trimethyllysine and histidine per mol of protein. Bovine, porcine, rabbit, rat and chicken brain calmodulins comigrated on polyacrylamide gels run under a variety of conditions in the presence and absence of denaturants. All brain calmodulins gave identical profiles for the Ca-dependent activation of activatable bovine brain 3'',5''-cyclic nucleotide phosphodiesterase. In addition, they formed Ca-dependent complexes with rabbit skeletal muscle troponin I and the electrophoretic mobilities of the complexes were identical with one another and similar to the corresponding complex between troponin I and troponin C. These studies more fully define a calmodulin, demonstrate that calmodulin is a relatively invariant constituent of vertebrate brain, and indicate that calmodulin structure and function have been highly conserved throughout vertebrate evolution.

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