The ATP-Binding Cassette Proteins of the Deep-Branching Protozoan Parasite Trichomonas vaginalis

Abstract

The ATP binding cassette (ABC) proteins are a family of membrane transporters and regulatory proteins responsible for diverse and critical cellular process in all organisms. To date, there has been no attempt to investigate this class of proteins in the infectious parasite Trichomonas vaginalis. We have utilized a combination of bioinformatics, gene sequence analysis, gene expression and confocal microscopy to investigate the ABC proteins of T. vaginalis. We demonstrate that, uniquely among eukaryotes, T. vaginalis possesses no intact full-length ABC transporters and has undergone a dramatic expansion of some ABC protein sub-families. Furthermore, we provide preliminary evidence that T. vaginalis is able to read through in-frame stop codons to express ABC transporter components from gene pairs in a head-to-tail orientation. Finally, with confocal microscopy we demonstrate the expression and endoplasmic reticulum localization of a number of T. vaginalis ABC transporters.

Localisation of a family of complex‐forming β‐barrels in the T. vaginalis hydrogenosomal membrane

“…In excavates this is not so apparent. Our analysis strongly supports the existence of an extended family of Tom40 like b-barrels in T. vaginalis, in contrast to trypanosomes which have a single ancestral b-barrel/ porin-like protein that is not clearly assigned as either VDAC or Tom40 [14][15]. The THOM proteins in T. vaginalis represent a single family of translocases within the hydrogenosome, and whilst this paper supports a similarity to Tom40, the absence of strong VDAC homologues could suggest either a functional differentiation of THOM proteins to fulfill VDAC functions, or that the THOM proteins represent an ancestral group of translocases, prior to the functional divergence of outer membrane b-barrels in other lineages.…”

“…Genomic DNA was extracted from T. vaginalis G3 as previously described [14] and DNA sequences for candidate THOM proteins were amplified using primers listed in Supplementary Table 1. THOM PCR products were inserted into a modified pTagVag2 [15] vector (a double haemaglutinin tag (HA–HA) being inserted in frame with the start codon) by restriction enzyme mediated sub‐cloning.…”

“…T. vaginalis strains ATCC30001 (C1) and G3 were maintained in Diamond's medium (TYM) supplemented with iron as previously described [13,14].…”

“…All constructs were validated by DNA sequencing across the entire coding region. T. vaginalis was transfected and selected with G418 as previously described [14].…”

The cell survival pathways of the primordial RNA-DNA complex remain conserved in the extant genomes and may function as proto-oncogenes

“…The fl agellated microaerophilic parabasalid trichomonas operates a functionally most complex ATP-binding cassette ABC transporter system [39]; its cytoplasm is well protected. The heavily duplicated trichomonas genome accepts and rejects horizontally transferred genes of prokaryotic derivation [40], carries dsRNA and totiviridae genomes [41][42][43], harbors inserted retrotransposons (Tc1/ mariner, Kolobok) [44,45], and practices morphological transformation of a fl agellate entity into an amoeboid parasite [46,47].…”