A 2ND MEROZOITE SURFACE PROTEIN (MSP-4) OF PLASMODIUM-FALCIPARUM THATCONTAINS AN EPIDERMAL GROWTH FACTOR-LIKE DOMAIN

Merozoite surface proteins of Plasmodium falciparum play a critical ro le in the invasion of human erythrocytes by the malaria parasite. Here we describe the identification of a novel protein with a molecular ma ss of 40 kDa that is found on the merozoite surface of P. falciparum. We call this protein merozoite surface protein 4 (MSP-4). Evidence for the surface location of MSP-4 includes (i) a staining pattern that is consistent with merozoite surface location in indirect immunofluoresc ent studies of cultured parasites, (ii) localization of MSP-4 in the d etergent phase in Triton X-114 partitioning studies, and (iii) nucleot ide sequencing studies which predict the presence of an N-terminal sig nal sequence and a hydrophobic C-terminal sequence in the protein. Imm unoprecipitation studies of biosynthetically labelled parasites with [ JH]myristic acid indicated that MSP-4 is anchored on the merozoite sur face by a glycosylphosphatidylinositol moiety. Of considerable interes t is the presence of a single epidermal growth factor-like domain at t he C terminus of the MSP-4 protein, making it the second protein with such a structure to be found on the merozoite surface.