Jason Arthur Smythe

Integral membrane protein located in the apical complex of Plasmodium falciparum

We describe the cloning of a novel antigen of Plasmodium falciparum which contains a hydrophobic domain typical of an integral membrane protein. This antigen is designated apical membrane antigen 1 because it appears to be located in the apical complex. Apical membrane antigen 1 appears to be transported to the merozoite surface near the time of schizont rupture.

Structural diversity in the 45-kilodalton merozoite surface antigen of Plasmodium falciparum

An integral membrane protein associated with the merozoite surface of Plasmodium falciparum termed merozoite surface antigen 2 (the 45-kDa merozoite surface antigen), occurs in antigenically diverse forms. Here we report the sequences of the MSA 2 gene from two other isolates of P. falciparum. The 43 N-terminal residues and the 74 C-terminal residues of all three MSA 2 sequences are highly conserved, but between these conserved regions there are dramatic differences among the alleles. Instead of the two copies of a 32-amino-acid repeat present in the MSA 2 of isolate FC27, MSA 2 from clone 3D7 and isolate Indochina 1 contain 5 and 12 copies respectively of the four amino acid sequence Gly Gly Ser Ala. The sequences flanking the repeats also differ among the three antigens. The repeats in MSA 2 appear to be immunodominant during natural infection, and antibodies to the repeat regions of different alleles react with a restricted number of parasite isolates.

Immunoblotting analysis of the major integral membrane protein antigens of Schistosoma japonicum

Triton X-114 has been employed to isolate integral membrane proteins from Schistosoma japonicum and Schistosoma mansoni adult worms. Suitable marker molecules and antisera directed or raised against schistosome proteins partitioned by Triton X-114 extraction indicated that the phase separation and purification of integral membrane proteins had been successful and this fraction was free of contamination with aqueous (soluble) or secretory antigens. Two dimensional immunoblots further exemplified differences between antigens in the integral membrane protein extract and those of the aqueous fraction. Seven S. japonicum integral membrane proteins have been identified on immunoblots by serum from a hyperimmune and an infected rabbit and by sera from Philippine patients with a history of schistosomiasis japonica. Integral membrane proteins of S. mansoni and S. japonicum had surprisingly little conformity in the molecular weights and electrophoretic mobilities between the two species.