Bovine plasma cold-insoluble globulin: gross structure and function.

Bovine plasma CIg, like human CIg, is a glycoprotein with a molecular weight of approximately 450,000 daltons and consists of two homologous subunits, the alpha and beta chains. These subunits are covalently linked through disulfide bridges in their carboxyl terminal domains. The carboxyl terminal regions are presumed to contain the fibrin-reactive transamidation site. The covalent incorporation of CIg into fibrin has been conclusively demonstrated by isolation of the S-carboxymethyl derivative of the CIg-fibrin-alpha chain complex and by determination of its terminal amino acid sequences. Cold-insoluble globulin has been shown to exert a stimulatory effect on the urokinase-mediated activation of bovine plasminogen to plasmin.