Purification and characterization of a matrix shell protein from the shell of scallop Patinopecten yessoensis

A new protein named MSP-SC (matrix shell protein from scallop) with a molecular weight of 14 kDa was isolated from the shell of a scallop, Patinopecten yessoensis, using gel filtration column chromatography, ion exchange column chromatography, and reverse phase C4 column chromatography. A comparison of the known protein sequences with the N-terminal sequence of MSP-SC showed that the protein sequence of MSP-SC was novel. Immunohistochemistry using a polyclonal antibody against MSP-SC showed that MSP-SC is expressed in the mantle pallial cell layer but not in the muscle tissue, and showed a punctate distribution along the horizontal calcified layer in the shell. The isolated MSP-SC inhibited the formation of calcium carbonate (CaCO3) crystals in a dose-dependent manner. The CaCO3 crystals grown in the presence of a lower concentration of MSP-SC were much larger and aggregated when compared with those formed in the absence of MSP-SC. In addition, the crystal had a radial and not cubical morphology. These results suggest that MSP-SC regulates the formation and the morphology of CaCO3 crystals in the shell. Moreover, its ability to aggregate CaCO3 crystals and its localization along the horizontal calcified layer in the shell suggest that MSP-SC may serve to connect the CaCO3 layers in the scallop shell.