Biosynthesis of the target antigens of antibodies blocking transmission of Plasmodium falciparum.

We have studied the biosynthesis of three proteins of Mr 260 000, 59 000 and 53 000 previously identified on the surface of extracellular gametes of Plasmodium falciparum as the targets of monoclonal antibodies which block infectivity of P. falciparum to mosquitoes. In cultures of P. falciparum pulse labeled with [35S]methionine we have found that these proteins are synthesized by gametocytes from an early stage in their maturation but are not synthesized by asexual blood stage parasites. The target proteins synthesized by the gametocytes become expressed on the surface of the extracellular gametes but the gametes themselves no longer synthesize these proteins. The 59 000 and 53 000 Mr proteins do not result from processing from the 260 000 Mr protein. The 59 000 and 53 000 Mr protein, but not the 260 000 Mr proteins, were glycosylated by either glucosamine or mannose.