Localization of the site of human transferrin interacting with cellular receptors using monoclonal antibodies

Antigenic determinants of the human transferrin molecule on the sublobe and lobe levels were localized for 7 monoclonal antibodies. Antibodies used have different effects on the interaction of the transferrin with its receptor. It was concluded that transferrin-receptor recognition was determined by NH2-lobe, the N2-sublobe playing major part. Dimerization of the transferrin molecules in solution was detected. Using the panel of monoclonal antibodies it was shown that dimerization accomplished by means of the COOH-lobes of transferrin molecules, the sites of interaction of the NH2-lobe with receptor being exposed. A model of the transferrin - receptor complex is proposed.