The surface protein repertoires of Cryptosporidium spp. and other apicomplexans.

Abstract

AbstractWhole-genome and high-coverage nucleotide sequence information is now available for three species of Cryptosporidium: C. parvum, C. hominis and C. muris. In this chapter I introduce the repertoires of Cryptosporidium surface and secreted proteins as revealed by complete annotations and whole-genome comparisons. These descriptions are also extended to comparisons with the apicomplexans, Plasmodium, Theileria and Toxoplasma, all of which have available complete nucleotide sequence information. Cryptosporidium possesses a large repertoire of multi-domain surface proteins that align it with the Coccidia, to the exclusion of Haemosporidia (Plasmodium spp.) and Piroplasmida (Theileria). The proposed phylogenetic affinity of Cryptosporidium with Gregarina indicates that these two early-diverging apicomplexans might uniquely share surface protein repertoires; however, analyses of sequence information from a GSS project for the gregarine, Ascogregarina taiwanensis, did not identify proteins that are conserved with Cryptosporidium to the exclusion of Toxoplasma. Cryptosporidium possesses numerous lineage-specific proteins, many of which are expanded within gene families and within loci of paralogous genes. These rapidly evolving surface proteins may have conferred adaptations to the specialized parasitic niche within the intestinal epithelium, and perhaps mediate direct physical interactions with the host. The lineage-specific proteins are conserved, perhaps without exception, in C. hominis, but are highly divergent and apparently not universally conserved as orthologues in the newly available genome nucleotide sequence database for C. muris.