Regular PaperMolecular characterization of a third malic enzyme-like AP65 adhesin gene ofTrichomonas vaginalis
Review articleOpen access

AbstractAdherence to the vaginal epithelium by the sexually transmitted parasiteTrichomonas vaginalisis mediated by four trichomonad surface proteins (AP65, AP51, AP33 and AP23). We recently showed that the 65-kDa adhesin is a member of a multigene family comprised of two similar but distinct proteins, AP65-1 and AP65-2, encoded by the genesap65-1andap65-2, respectively. An additional immuno-crossreactive clone, the 1.2 kb F11.1 cDNA, was isolated from a phagemid expression library and encoded a fusion protein of ≈ 46 000 daltons (46 kDa) that bound to HeLa cell surfaces. A significant portion of the 5′ end was missing which, using the 5′-RACE method, was obtained and combined with the F11.1 clone to give a full-length cDNA. Theap65-3gene encoded for a protein of 567 amino acids with a molecular mass of 63.1 kDa. The gene showed 88% and 96% identity at the DNA level withap65-1andap65-2, respectively. Restriction mapping confirmed that the three AP65 genes are different. Southern analysis revealed that theap65-3gene is present in theT. vaginalisgenome in multiple copies. Experiments with agar clones of trichomonads showed that each gene of the multigene family is present in all parasites, and Northern analysis showed thatap65-3is expressed and transcriptionally regulated by iron. Theap65-3gene had a leader sequence and, as withap65-1andap65-2, showed significant homology to malic enzyme. Finally, analysis of the 3′-untranslated regions revealed that the transcript ofap65-3had a long poly (A) tail in comparison toap65-1andap65-2. Even more intriguing, sequences were found that may relate to differential degradation of select AP65 transcripts, such as the sequence motifs AUUUA forap65-1mRNA and UUAUUUAU for theap65-2mRNA, which were not found forap65-3.

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