Caldesmon

Abstract Smooth muscle caldesmon isolated from chicken gizzard migrates with an apparent molecular weight of 14 000 on SDS gels; cDNA sequencing gives molecular weights of 93 kDa for human and 89 kDa for chicken gizzard caldesmon. The protein sequence shows a long central α-helical region containing a repeated 13 (or 15) amino acid motif; the number of repeats is 8–12, depending on the degree of degeneracy allowed. Circular dichroism measurements of a central fragment are consistent with a helical structure. The 60 174 Da non-muscle caldesmon (I-CaD, for its lower molecular weight) is smaller than the muscle isoform; cDNA sequencing of an I-CaD indicates deletion of 232 amino acids beginning near residue 200 and including the region of repeats.