Peptide digest studies of polymorphic proteins of Plasmodium falciparum

Previous work has shown that when a large number of Plasmodium falciparum isolates are examined by two dimensional electrophoresis, over 100 different proteins can be detected, 15 of which show polymorphism in electrophoretic characters. Eight of these proteins have now been subjected to limited proteolysis. Two methods of digestion were used: enzymic, with Streptomyces griseus Pronase E and chemical, using N-chlorosuccinimide to break proteins at tryptophan residues. When different forms of each variable protein were analysed most were found to exhibit similar peptide profiles, a finding indicating that they were determined by alleles of genes at single loci. Two of the proteins, A and K, exhibited higher degrees of polymorphism than the other variable proteins. The possible reasons for this are discussed.