A MONOCLONAL-ANTIBODY RECOGNIZING A CONSERVED EPITOPE IN A GROUP OF PHOSPHOLIPASES-A2

Notexin and nigexine are monomeric phospholipases A2(PLA2s) from the venoms of Notechis scutatus scutatus and Naja nigricollis, respectively. Polyclonal antibodies raised in mice against these antigenic proteins displayed non-reciprocal cross-reactivity; anti-notexin antibodies recognized notexin but not nigexine, whereas anti-nigexine antibodies recognized both antigens. Polyclonal antibodies raised by successive immunization with nigexine and notexin contained cross-reacting antibodies with affinities for both antigens that differed from those of antibodies present in anti-nigexine antiserum. A monoclonal antibody has been obtained from a mouse immunized with both PLA2s. This monoclonal antibody, called MN1, recognized notexin and nigexine with comparable high affinity (Kd=10-9 M). It also recognized most purified PLA2s from elapid snake venoms and all PLA2-containing venoms from cobras and sea-snakes. This offers the first demonstration that most PLA2s from cobras and sea-snakes share a fine structure which is not restricted to the common catalytic site. © 1990.