INFLUENCE OF ANTIBODY-BINDING ON OXYGEN-BINDING BEHAVIOR OF PANULIRUS-INTERRUPTUS HEMOCYANIN

Oxygen binding behavior of monomeric subunit a and the hexameric form of this subunit of hemocyanin of Panulirus interruptus is influenced b y the binding of various monoclonal antibodies. These antibodies react with other surface parts of the subunit than its second domain in whi ch the oxygen binding site is located. The influence of three monoclon al antibodies and their antigen binding fragments (F-ab) has been inve stigated. Two antibodies increase the oxygen affinity of monomeric hem ocyanin from that observed in its low affinity T-state, while the thir d has little influence on this property. F-ab fragments abolish almost completely the cooperativity of oxygen binding by the hexameric hemoc yanin molecule. The two antibodies which increase the oxygen affinity of the monomeric molecule stabilize high-affinity states of the hexame ric molecule, while the third stabilizes the low-affinity state. (C) 1 997 Federation of European Biochemical Societies.