Turkey gizzard caldesmon: complete sequence of a C-terminal thrombic fragment that binds actin, tropomyosin and calmodulin.
We have determined, by protein chemistry methods, the complete amino acid sequence of a thrombic fragment, "CaD35", which contains the C-terminal 274 residues of turkey gizzard caldesmon. Residues 1-96 of CaD35 comprise an actin-binding subfragment which resembles the tropomyosin-binding segment of troponin T. Residues 111-128 and 255-272 may form basic, amphipathic helices that interact with calmodulin. Residues 251-253 (Ser-Ser-Ser) may be phosphorylated. Chymotryptic CaD35, obtained from chicken gizzard caldesmon, nearly identical in sequence to the turkey gizzard fragment, but contains an additional 32 amino acid residues at its N terminus.