SEQUENCE AND ATOMIC-FORCE MICROSCOPY ANALYSIS OF A MATRIX PROTEIN FROM THE SHELL OF THE OYSTER CRASSOSTREA-VIRGINICA

Atomic-force microscopy of the major class of soluble matrix protein from the oyster Crassostrea virginica revealed that this protein forms a ring structure, perhaps rendering the NH2-terminus unavailable to Edman degradation. Cleavage of these proteins using mild acid hydrolysis and hydroxylamine produced linear peptides that were able to be sequenced. Peptides consisted of a domain of polyserine-phosphoserine and runs of aspartic acid of 4 to 7 residues, with several other amino acids present. Hydrophobic domains were also isolated. Although phylogenetically distant, oyster shell-matrix protein is similar to the phosphophoryn isolated from dentin and, to a lesser extent, proteins isolated from vertebrate bone.