A vacuolar-type proton (H+) translocating ATPase α subunit encoded by the Hc-vha-6 gene of Haemonchus contortus

In the present study, a full-length cDNA (designated Hc-vha-6) inferred to encode an α subunit of a vacuolar-type proton translocating adenosine triphosphatase (V-ATPase) was isolated from the parasitic nematode Haemonchus contortus, and characterized. The transcript for Hc-vha-6 was detected in all developmental stages and both sexes of H. contortus. Elements, including two TATA box (TATAA), two inverted CAAT box (ATTGG), five E box (CANNTG) and six GATA as well as five inverse GATA (TTATC) transcription factor motifs, were identified in the non-coding region upstream of Hc-vha-6. The open reading frame (ORF) of 2601 nucleotides encoded a protein (Hc-VHA-6) of 866 amino acids and a molecular weight of ∼98.7 kDa. Comparison with a published protein sequence for a homologue (VPH1P) from yeast showed that Hc-VHA-6 had nine transmembrane domains and the 14 essential amino acid residues associated with enzyme activity, assembly, intracellular and/or membrane targeting. Phylogenetic analyses of selected amino acid sequence data revealed Hc-VHA-6 to be most closely related to VHA-6 of Caenorhabditis elegans. A predictive network analysis inferred that vha-6 interacts with at least seven other genes encoding V-ATPase subunits and a small Rab GTPase. This study provides the first insight into a V-ATPase of parasitic nematodes and a sound basis for future functional genomic work.