Plasmodium knowlesi:Secondary Processing of the Malaria Merozoite Surface Protein-1

Abstract

Blackman, M. J., Dennis, E. D., Hirst, E. M. A., Kocken, C. H., Scott-Finnigan, T. J., and Thomas, A. W. 1996.Plasmodium knowlesi:Secondary processing of the malaria merozoite surface protein-1.Experimental Parasitology83,229–239. Secondary processing of thePlasmodium falciparummalaria merozoite surface protein-1 (MSP-1) is defined as a single proteolytic cleavage within the carboxy-terminal membrane-bound component of the MSP-1 protein complex on the free merozoite surface. The N-terminal cleavage product (MSP-133) is shed from the parasite surface along with a number of other polypeptides, whereas the C-terminal processing product remains bound to the merozoite surface and is the only part of MSP-1 detectable in the newly invaded host cell. We report that secondary processing of MSP-1 takes place in a similar manner on invasive merozoites of the simian malaria parasitePlasmodium knowlesi.Processing can take place to a limited extent in pure isolated merozoites; however, within 10 min of the addition of purified invasive merozoites to rhesus erythrocytes, processing and shedding of MSP-1 has gone to completion only in those parasites which have undergone invasion; residual free merozoites remain uniformly reactive with antibodies against MSP-133. Successful invasion is therefore associated with complete shedding of MSP-133from the merozoite surface. The nucleotide sequence of the 3′ domain of theP. knowlesiMSP-1 gene is also presented.