FIG. 1.

Schematic outline of MSP-1D. The precursor of MSP-1D is a protein comprising 1,720 amino acids, including a 20-amino-acid signal sequence (SS) and a signal for anchoring the protein at the cellular surface via a GPI moiety (GA). The precursor is processed into four major products, p83, p30, p38, and p42, as indicated by arrows. In a second proteolytic step, p42 is cleaved into p33 and p19. Primary sequences of MSP-1 from different strains follow distinct patterns of conservation. As indicated, there are regions of high conservation (white) and regions that are essentially dimorphic (grey), classifying the molecule as a member of either the K1 or the MAD20 family (32, 46). In addition, there are two short oligomorphic areas, block II and block IV (46). MSP-1D of strain 3D7 belongs to the MAD20 family, with the exception of block II, which is K1-like.