cDNA clonings of shell matrix proteins from scallop shell

A cDNA encoding the matrix shell protein from scallop (MSP-2) has been cloned. Comparison of the sequence of MSP-2 with the GenBank database revealed the sequence displays a high degree of homology with MSP-1, which was recently identified in the shell of the scallop Patinopecten yessoensis. Matrix shell protein-2 contains only 323 amino acids, while MSP-1 comprises 824 amino acids. The structural difference between MSP-1 and MSP-2 is mainly the presence or absence of the tandem repeat arrangement. In addition, multiple isoforms of MSP-2 were found. These isoforms share a high degree of sequence similarity to each other, suggesting that the MSP-2, MSP-2 isoforms and MSP-1 may constitute the same family. The MSP-2 isoforms in scallop shell may be responsible for the formation of molluscan shells.