Identification and quantification of histidine-rich glycoprotein (HRG) in the blood plasma of six marine bivalves.

Histidine-rich Glycoprotein (HRG) is a metal-binding protein described from the blood plasma of a pteriomorph bivalve, the marine mussel Mytilus edulis L. We demonstrate here, using Cd-Immobilized Metal Affinity Chromatography (IMAC), SDS-PAGE, Western Blotting, and ELISA, that HRG is present in three additional pteriomorphs and two heterodont bivalves. ELISA indicates that HRG is the predominant blood plasma protein in all six species (41 to 61% of total plasma proteins by weight). Thus, HRG appears to be a widespread metal-binding protein in the plasma of bivalves.