Molecular analysis of the gene encoding the immunodominant phenotypically varying P270 protein of Trichomonas vaginalis

Abstract

Trichomonas vaginalisis a flagellated protozoan responsible for the most common non-viral sexually transmitted disease. The immunogen P270 was previously found to be up-regulated in expression and to undergo phenotypic variation between surface versus cytoplasmic localization in trichoImonads harbouring a dsRNA virus. In this report, we characterize the entire p270 open reading frame (ORF) and the unknown flanking 5;- and 3;-unique, non-repeat coding sequences of the gene in addition to untranslated regions. Consistent with an earlier report (Dailey & Alderete, 1991, Infect. Immun. 59: 2083-88), a significant portion of the gene consists of a tandemly repeated 333 bp element that contains the sequence coding for the epitope DREGRD detected by murine monoclonal antibody and antibody from the sera of patients. The non-repeat coding regions for the 5;- and 3;-ends were 69 nucleotides (23 amino acids) and 1183 nucleotides (395 amino acids), respectively. Sequencing of repeat elements showed them to be identical, affirming the highly-conserved nature of this element throughout the gene. The start codon was immediately preceded by the 12 nucleotide consensus sequence (TCATTTTTAATA) found in other trichomonad protein-coding genes. A very AT-rich, non-coding region was identified upstream of the p270 ORF. P270 appears to contain a leader sequence at the amino-terminus and transmembrane domain at the carboxy-terminus. No significant homology was found with any reported proteins at either the nucleotide or amino acid level.