Species comparison of calmodulin sequences.

No amino acid substitutions can be located when the calmodulin produced in various vertebrate species (human, rat, chicken, toad) are compared. However, multiple substitutions exist in calmodulin derived from non-vertebrates. Here, we have determined the residues for which no alterations in sequence are allowed. The protein from each species exhibits a sequence identity from residue 27 to residue 53, i.e., residues spanning a small part of the Ca2+ binding loop I and the adjacent interloop region. The analogous sequence (residues 100 to 129) abutting the Ca2+ binding loop III also exhibits only a few differences. Furthermore, negatively charged side chains at residues 82-84 in the central alpha-helix are conserved.