CLOSE LINKAGE OF 3 MEROZOITE SURFACE PROTEIN GENES ON CHROMOSOME-2 OFPLASMODIUM-FALCIPARUM

We have analysed a 10.5 kb region of chromosome 2 in Plasmodium falcip arum that encompasses the coding region of four genes. Three genes are arranged in a head-to-tail orientation and encode the merozoite surfa ce proteins MSP2 and MSP4 as well as a previously unreported sequence that encodes a polypeptide with the characteristics of a merozoite sur face protein, now designated MSP5. The fourth gene, asl, is arranged i n a tail-to-tail orientation with msp2 and has homology with prokaryot ic and eukaryotic genes encoding adenylosuccinate lyase (ASL), an enzy me involved in purine biosynthesis and salvage. The genes, arranged in the order msp4, msp5, msp2 and asl, are separated by intergenic dista nces of 1021, 1017 and 722 bp, respectively. msp4 and msp5 are clearly related genes, each being composed of 2 exons and encoding proteins o f identical length. Both msp4 and msp5 encode proteins that contain hy drophobic signal sequences, apparent glycosylphosphatidylinositol (GPI ) attachment signals and a single epidermal growth factor-like (EGF-li ke) domain at their carboxyl termini. Nevertheless, the remainder of t heir protein coding regions are quite dissimilar. It appears that one of these genes arose as a result of a relatively ancient gene duplicat ion event and both genes have subsequently diverged considerably. This study shows that msp5 is transcribed in asexual stages and its encode d product is a 40 kDa protein that appears to be located on the merozo ite surface as determined by immunofluorescence assays. (C) 1998 Elsev ier Science B.V. All rights reserved.