The production and characterization of monoclonal antibodies to rabbit histidine-rich glycoprotein and hemopexin
McConnell, Jennifer L.
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Heme and metals are bound to specific serum proteins for transport in the serum. Histidine-Rich Glycoprotein (HRG), MW 94,000, does not have a well-defined physiological role, although it is thought to function in divalent metal transport and fibrin clotting. Hemopexin (Hx), MW 60,000, binds heme released from hemoglobin and transports it to the liver, where the heme-hemopexin complex is bound to specific receptors on the hepatocyte membrane. Cleavage of Hx with plasmin produces two peptides. Domain I, MW 35,000, binds heme, whereas domain II, MW 25,000, does not. In order to further study the function of HRG and Hx, two monoclonal antibodies were produced to rabbit HRG, and eight monoclonal antibodies were produced to rabbit Hx. Competitive binding assays with anti-Hx monoclonals indicate that four bound antigenic determinants on Hx and domain I, one bound an antigenic determinant on Hx and domain II, and two bound antigenic determinants on Hx only.