Structure and transcription of a P-ATPase gene from Trypanosoma brucei

A putative ATPase gene was cloned from Trypanosoma brucei genomic DNA. The length of the gene open reading frame is 3,033 bp, predicting a protein of about 110 kDa. The sequence of this protein shares 10 blocks of homology with other eukaryotic ATPases, including the putative phosphorylation site characteristic of P-ATPases. Its hydropathy profile reveals 8-10 potential membrane-spanning regions. While the amino acid sequence of the T. brucei ATPase shows only 25% overall homology with its counterpart from the related kinetoplastid protozoan Leishmania donovani, 49% sequence conservation is found when compared with the calcium-ATPase from rabbit sarcoplasmic reticulum. This gene is present in only one copy, localized in the large chromosome fraction. It is transcribed at a similar level in procyclic and bloodstream forms, as a 4.3-kb mRNA. Run-on assays suggest continuous transcription of the gene and flanking sequences over at least 10 kb, by a RNA polymerase sensitive to alpha-amanitin. Transcription inhibition by UV irradiation suggests that the ATPase gene is more than 4 kb downstream from its promoter.