Modification of calmodulin function by enzymatic carboxyl methylation

Calmodulin is a ubiquitous calcium-binding protein that regulates a variety of enzymes such as adenylate cyclase, cyclic nucleotide phosphodiesterase, ATPase and protein kinase. So far, no enzymatic modification of calmodulin has been shown to affect its function. Another ubiquitous protein, the enzyme protein-carboxyl methylase (PCM), modifies proteins post-translationally by methylating their free carboxyl groups and thus neutralizing negative charges. This enzyme is one of three elements of the protein-carboxyl methylation system; the two others are the substrates, the methyl acceptor proteins (MAP) and the demethylating enzyme, protein methylesterase (PME). We report here that calmodulin is an exceptionally good substrate for PCM and that the enzymatic post-translational methylation of calmodulin inhibits its stimulatory effect on cyclic nucleotide phosphodiesterase. Furthermore, we present evidence that carboxyl methylation of calmodulin occurs in intact cells.

Duke Scholars

Author Warren James Strittmatter Neurology, Behavioral Neurology