Physical and chemical characterization of an oyster hemagglutinin.

The natural hemagglutinin of the oyster Crassosfrea virginica was examined for possible structural relationship with vertebrate immunoglobulins. The hemagglutinin activity was associated with a heterogeneous group of rapidly sedimenting molecules. The major active component in oyster hemolymph has a sedimentation coefficient of 33.4 S, but minor components with lower sedimentation coefficients are also present. The molecules can be dissociated into subunits consisting of single polypeptide chains having an approximate molecular weight of 20,000. Complete dissociation could be observed in 5 M guanidine-HCl indicating noncovalent linkage of the subunit. Amino acid composition of the subunit was distinguished by a relatively high histidine content and the absence of lysine. The sequence of the first 2 residues from the NH, terminus of the subunit was found to be Thr-Ala. Mannose, galactose, and glucosamine were present with a total carbohydrate content of 13%. These data do not demonstrate obvious structural similarities to mammalian immunoglobulins.