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The phenotypically variable surface protein of Trichomonas vaginalis has a single, tandemly repeated immunodominant epitope.

ABSTRACT: Trichomonas vaginalis is a sexually transmitted protozoan parasite that undergoes phenotypic variation for numerous surface proteins. A monoclonal antibody (MAb) was used to isolate an approximately 400-bp cDNA encoding a fragment of an important phenotypically varying immunogen of T. vaginalis (Mr = 270 kDa; P270). The MAb completely inhibited the binding of P270 by antibody in sera of patients and by antibody in monospecific antiserum obtained toward purified P270, indicating that P270 contained only one immunodominant epitope. Hydrophilicity plot analysis of the deduced amino acid sequence of the recombinant protein predicted the hexapeptide sequence DREGRD as the antigenic determinant of P270. Synthetic peptides synthesized to this region demonstrated that the amino acid sequence DREGRD is important for antibody binding. Seven adjacent amino acids also contributed substantially to maximal recognition of the epitope by the MAb. A single transcript of approximately 9.5 kb, a size compatible with the reported Mr of the immunogen, hybridized to the cDNA in Northern blots of total RNA from T. vaginalis. DNA sequence and Southern blot analysis determined the epitope to be encoded by a 339-bp unit, which was found to be tandemly repeated at least 12 times within the single-copy gene. This 12-mer unit would only constitute approximately 50% of the protein, yet it is responsible for all of the serum antibody to the immunogen produced by animals and humans. The epitope sequence was found in all fresh and long-term-grown organisms examined to date, demonstrating the stability and conservation of this gene.

SUBMITTER: Dailey DC

PROVIDER: S-EPMC257969 | biostudies-other | 1991 Jun

REPOSITORIES: biostudies-other

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The phenotypically variable surface protein of Trichomonas vaginalis has a single, tandemly repeated immunodominant epitope.

Dailey D C DC Alderete J F JF

Infection and immunity 19910601 6

Trichomonas vaginalis is a sexually transmitted protozoan parasite that undergoes phenotypic variation for numerous surface proteins. A monoclonal antibody (MAb) was used to isolate an approximately 400-bp cDNA encoding a fragment of an important phenotypically varying immunogen of T. vaginalis (Mr = 270 kDa; P270). The MAb completely inhibited the binding of P270 by antibody in sera of patients and by antibody in monospecific antiserum obtained toward purified P270, indicating that P270 contain ...[more]

PMID: 1709920

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Project description:Ornithine decarboxylase (ODC), the lead enzyme in polyamine biosynthesis, was partially purified from Trichomonas vaginalis and its kinetic properties were studied. The enzyme appears to be of special significance in this anaerobic parasite, since the arginine dihydrolase pathway generates ATP as well as putrescine from arginine. ODC from T. vaginalis had a broad substrate specificity, decarboxylating ornithine (100%), lysine (1.0%) and arginine (0.1%). The enzyme had a pH optimum of 6.5, a temperature optimum of 37 degrees C and was pyridoxal 5'-phosphate-dependent. Attempts to separate ornithine- from lysine-decarboxylating activity by thermal-stability and pH-optima curves were not successful. Although Km values for ornithine and lysine were 109 and 91 microM respectively, and the Vmax values for these substrates were 1282 and 13 nmol/min per mg of protein respectively, the most important intracellular substrate is ornithine, since intracellular ornithine levels are 3.5 times those of lysine and extracellular putrescine levels are 7.5 times those of cadaverine. Ornithine was also an effective inhibitor of lysine-decarboxylating activity (Ki 150 microM), whereas lysine was relatively ineffective as inhibitor of ornithine-decarboxylating activity (Ki 14.5 mM). Crude ODC activity was localized (86%) in the 43,000 g supernatant and 3303-fold purification was obtained by (NH4)2SO4 salting and DEAE-Sephacel, agarose-gel and hydroxyapatite chromatography steps. The enzyme bound difluoro[3H]methylornithine ([3H]DFMO) with a ratio of drug bound to activity of 2500 fmol/unit, where 1 unit corresponds to 1 nmol of CO2 released from ornithine/min. The enzyme had a native M(r) of 210000 (gel filtration), with a subunit M(r) of 55,000 (by SDS/PAGE), suggesting that the trichomonad enzyme is a tetramer. From the subunit M(r) and binding ratio of DFMO, there is about 137 ng of ODC per mg of T. vaginalis protein (0.013%). The significant amount of ODC protein present supports the view that putrescine synthesis in T. vaginalis plays an important role in the metabolism of the parasite.

Dataset Information

The phenotypically variable surface protein of Trichomonas vaginalis has a single, tandemly repeated immunodominant epitope.

Publications

The phenotypically variable surface protein of Trichomonas vaginalis has a single, tandemly repeated immunodominant epitope.

Similar Datasets

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