Methionine 156 in the immunodominant domain of CD36 contributes to define the epitope recognized by the NL07 MoAb.

Abstract

CD36 is a membrane glycoprotein expressed by several cell types, and play a role as a receptor for different physiological and pathological ligands. An immunodominant domain of CD36 has been described in the amino acidic region 155-183, where many ligands and monoclonal antibodies (MoAbs) react. MoAbs against CD36 have proved useful in structural as well as functional studies. One of these antibodies, MoAb NL07, recognizes a conformational epitope that is acquired in the late steps of the CD36 maturation. The NL07 epitope appears to be functionally relevant and blocks CD36-mediated binding to red blood cells infected with the malaria parasite Plasmodium falciparum (IRBC). In this work a mutant COS-7 clone expressing NL07-negative CD36 molecules on the cell surface was investigated. In the mutant, the methionine in position 156 of the wild type CD36 sequence was replaced by a valine. It was determined that methionine 156 was essential for NL07 reactivity, mapping the NL07 epitope to the vicinity of the functionally important immunodominant domain (aa 155-183) of CD36. Although methionine 156 is located in this region, the CD36V156 mutated molecule was apparently functional and able to bind IRBC and oxidized LDL.