Identity of K+ channel homologues in pathogenic protozoa.

Protein accession numbers are shown and NF denotes that no homologues were found. Number of predicted TMDs is indicated in parentheses. K+ channel homologues are classified on the basis of closest similarity to a particular subtype of human K+ channel subunit and according to the presence of characteristic functional domains, such as a charged TMD4 (Kv), the presence of a cyclic nucleotide-binding domain CNBD (KCNG), or the presence of RCK domains (KCa). Where a protein showed similarity to more than one class of K+ channel, its accession number is shown in both relevant columns (eg. all Kv homologues are also KCa homologues).*KCNG homologues which contain a CNBD, but also a charged TMD4;alikely non-selective or non-functional due to GYRD, GYSD or GYSE selectivity filter motifs;bno putative RCK domains or calmodulin-binding domains (CaMBDs) were detected in these proteins by searching the Conserved Domains Database, but in BLASTP searches of the human genome these proteins showed greatest sequence similarity to the KCa channel subtypes indicated in parentheses. The P. falciparum proteins XP_001609692 and XP_001350669 are identical to the previously described PfKch2 and PfKch1 proteins respectively [14], [16]. The B. bovis (XP_001610013) and C. hominis (XP_668687) proteins have been identified previously as orthologues of PfKch1 in P. berghei[16]. In addition to the K+ channel homologues shown, homologues of putative adenylyl cyclase/K+ channel fusion proteins [123], [124] that contain GXG motifs after their TMD6 domains were also identified in P. falciparum (XP_001348216), P. knowlesi (XP_002260946), P. vivax (XP_001616904), T. gondii (XP_002368352, XP_002370938 and XP_002367966), C. muris (XP_002140763), C. hominis (XP_666311) and C. parvum (XP_626352). Homologues of these proteins were absent in all other parasites examined.