Purification and physical chemical characterization of 23S glycoprotein from sea urchin (Anthocidaris crassispina)...

A large glycoprotein with a sedimentation coefficient, S(0)20,w, of 23.3S was purified to homogeneity from sea urchin eggs (Anthocidaris crassispina) by gel filtration on Sepharose CL-4B and ion-exchange chromatography on DEAE-cellulose. The molecular weight of the protein was 700,000 as determined by sedimentation equilibrium. On polyacrylamide gel electrophoresis with sodium dodecyl sulfate (SDS) it showed a single band with an apparent molecular weight of 180,000 or 360,000 in the presence or absence of 2-mercaptoethanol, respectively. The protein consisted of four polypeptides of equal molecular weight, which were disulfide bonded in pairs. Its carbohydrate content as determined by the phenol-sulfuric acid method was 20% of the total weight. The amino acid and carbohydrate compositions, circular dichroic spectrum and electron microscopic image are also presented. The protein showed many structural similarities with the previously purified major glycoprotein (MCP) in the coelomic fluid of the same animal in addition to being immunologically cross reactive with it. However, the two proteins were distinct glycoproteins. Their biological functions have not been identified.