Amino acid sequence of the beta chain of sarcoplasmic calcium binding protein (SCP) obtained from shrimp tail muscle.

The amino acid sequence of the beta chain of shrimp SCP has been determined. It is composed of 192 amino acid residues and is acetylated at the N-terminus. The molecular weight was determined to be 21,960. The sequence difference with the aB chain of the same shrimp, of which the sequence was determined previously (J Biochem. (1984) 95, 1603-1615), is 19% (37 non-identical residues out of 192 residues). The shrimp SCPs have three EF-hand type Ca2+ binding sites, however, from comparison with the amino acid sequences of SCPs of scallop (Takagi et al., Biochim. Biophys. Acta in press) and of sandworm (Kobayashi et al., manuscript in preparation), it is reasonable to think that SCP originally had four Ca2+ binding sites, and in the case of shrimp SCPs, one of them (site IV) may have lost the affinity to Ca2+ on amino acid replacements during evolution.