This sequence differs from other calmodulin sequences by at least 13%. Many of the differences are non-conservative and some probably render the first and fourth potential calcium-binding regions nonfunctional. The authors' data suggest that there are at least two different calmodulin genes in the chicken genome, CCM1 and CCL1. Whereas CCL1 is thought to be the primary gene responsible for production of calmodulin, CCM1 codes for the sequence shown and is expressed only in cardiac and skeletal, not smooth, muscle. Belongs to the calmodulin family.