ISOLATION AND STUDY OF A FRAGMENT OF HUMAN SERUM ALBUMIN CONTAINING ONE OF THE ANTIGENIC SITES OF THE WHOLE MOLECULE

Abstract

A fragment of human serum albumin called ''inhibitor'' has been degraded by trypsin, and one of the degradation products, designated fragment F1, has been isolated. Fragment Fl has a molecular weight of 6600. It contains neither tyrosine nor tryptophan. It is not precipitated with rabbit anti-sera to human serum albumin. Fragment Fl was coupled to p-amino-benzylcellulose to form an insoluble conjugate. Rabbit anti-(human serum albumin) antibodies reacting with fragment Fl were specifically adsorbed on this conjugate and were desorbed by glycine-hydrochloric acid buffer. The isolated antibodies are composed of [gamma]-globulin and [beta]2-macroglobulin. Human serum albumin and fragment Fl formed with 7s anti-(fragment Fl) antibodies soluble complexes that were studied by passive haemagglutination, ultracentrifugation and electrophoresis. Fragment Fl was shown to contain only one of the antigenic sites of albumin molecule. The 7s anti-(fragment Fl) antibodies were shown to be bivalent and monospecific.