Trichomonas vaginalis has two fibronectin-like iron-regulated genes

Trichomonas vaginalis, a protozoan parasite of the human urogenital tract, interacts with fibronectin (FN), a glycoprotein of the extracellular matrix. We, therefore, attempted to identify genes of this eukaryote encoding FN-binding proteins.

A cDNA clone, C1, representing an incomplete gene was obtained from an expression library based on its FN-binding ability and was characterized. The full-length 378-bp gene encoding a 14.8-kDa protein of 125 amino acids was obtained.

The amino acid sequences revealed homology with the type III-14 repeat of the heparin-binding domain at the carboxyl terminal end of FN. This fibronectin-like protein gene, flp1, was single copy in all the T. vaginalis isolates examined. Levels of flp1 transcript were elevated in cells grown under low-iron conditions. Another low-iron-regulated gene, flp2, with 70 and 67.5% identity to flp1 at the nucleotide and amino acid levels, respectively, was recovered from the trichomonad genome. Both flp1 and flp2 had consensus Inr promoter-like elements immediately adjacent to the start codon. flp2 also contained an additional Inr element followed by an ATG 24-bp within the gene.

Unlike flp2, the flp1 gene had AU-rich destabilizing elements in the 3'-untranslated region (UTR).