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Further Characterization of Calmodulin from the Monocotyledon Barley (Hordeum vulgare) ¹

Laboratory of Cellular and Molecular Physiology, Howard Hughes Medical Institute, Vanderbilt University, Nashville, Tennessee 37232, Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232

We report here that calmodulin isolated from the monocotyledon barley is indistinguishable by a variety of criteria from calmodulin isolated from the dicotyledon spinach. In contrast to previous reports, we find that barley (Hordeum vulgare) calmodulin has an amino acid composition similar to that of vertebrate and spinach calmodulins, including the presence of a single trimethyllysinyl residue, and that barley calmodulin quantitatively activates cyclic nucleotide phosphodiesterase. Furthermore, spinach and barley calmodulins are similar in terms of tryptic peptide maps and immunoreactivity with various antisera that differ in their molecular specificities for calmodulins. Limited amino acid sequence analysis demonstrates that the region around the single histidinyl and trimethyllysinyl residues is identical among barley, spinach, and vertebrate calmodulins and that barley calmodulin, like spinach calmodulin, has a novel glutamine residue at position 96. We conclude that calmodulin is highly conserved among higher plants and that detailed sequence analysis is required before significant differences, if any, can be assigned to barley or other higher plant calmodulins. These studies suggest that calmodulin's fundamental importance to the eukaryotic cell may have been established prior to the evolutionary emergence of higher plants.

¹ Supported in part by National Science Foundation grant PCM 8242875. The costs of publication of this article were defrayed in part by page charges. This article must therefore be marked `advertisement' in accordance with 18 UCC Section 1734 solely to indicate this fact.