Evolution and expression of the Leishmania surface proteinase (gp63) gene locus

The Leishmania surface proteinase, gp63, is the most abundant, surface-exposed protein on the promastigote form of the parasite. It is the product of a multigene family that, in some Leishmania species, shows marked heterogeneity among its members. The differential expression of structurally distinct gp63 genes shows circumstantial correlation with the differential processing and localization of the protein in the intracellular, amastigote form of Leishmania mexicana. The recent cloning and sequencing of a homologous gene in the monoxenous trypanosomatid, Crithidia fasciculata, provides a reference sequence for comparison with ten Leishmania gp63 genes sequenced to date. The amino terminal and the carboxy terminal regions of the protein sequences suggest different evolutionary histories within some of the genes. The evolutionary significance of the structure, organization, and regulation of the gp63 genes from different Leishmania species is described and speculated upon.