Aspartyl proteinase genes from apicomplexan parasites: evidence for evolution of the gene structure

Aspartyl proteinases are a widely distributed family of enzymes. All verteb rate aspartyl proteinases share a conserved nine-exon gene structure, but i n other organisms the structure of aspartyl proteinase genes varies conside rably. The exon-intron patterns generally reflect phylogeny based on amino acid sequences. However, close comparison of these gene structures reveals some striking features, such as the conservation of intron positions and in tron phases between aspartyl proteinases from nematodes and apicomplexans. Here, we discuss the implications of gene structure for the possible evolut ion of the aspartyl proteinase family, with particular reference to the pla smepsins of Plasmodium falciparum and eimepsin from Eimeria tenella.