Metallothioneins (MTs) have been identified in a wide variety of organisms from bacteria to humans. The biological functions of these MTs have a key role in metalloregulatory metabolism and its expression is induced in response to different stimuli, particularly by divalent metal cations. Also, the action of MTs have been implicated in the survival of pathogens in presence of microbicidal concentration of divalent cations, which allows the establishment of the infection. Trichomonas vaginalis is a protozoan parasite that adapts to the microenvironment of the male urogenital tract, where cations such as zinc (Zn2+) and cadmium (Cd2+) are present. Nevertheless, the molecular mechanisms of metal tolerance and homeostasis is not yet dilucidated in this parasite. In this study, we have identified 4 potential MT-like sequences (tvmt´s) in T. vaginalis genome. Because tvmt-2, -3, and -4 corresponds to truncated partial genes, we characterized the trichomonad tvmt-1 gene. The bioinformatic analyses and the predicted protein (TvMT-1) show similar properties to the reported in other MTs. The expression patterns of tvmt-1 in the presence of several divalent cations (Fe2+, Mn2+, Zn2+ and Cd2+) were analyzed and we demonstrated that Cd2+ induce significantly their expression. By indirect immunofluorescence assays, we corroborated this positive regulation of TvMT-1 in the cytoplasm of parasites grown in the presence of Cd2+. The tvmt-1 promoter contains putative metal responsive elements, which are probably the responsible for the Cd2+-dependent expression of this gene. Our results suggest that tvmt-1 gene encode a metallothionein that may be responsible for the homeostatis and detoxification of Cd+2 in T. vaginalis.

中文翻译：

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在阴道毛滴虫中鉴定出的新型金属硫蛋白的镉依赖性表达。

金属硫蛋白（MTs）已在从细菌到人类的多种生物中得到鉴定。这些MT的生物学功能在金属调节代谢中起关键作用，并且其表达是响应于不同的刺激而被诱导的，特别是通过二价金属阳离子。同样，在杀微生物浓度的二价阳离子存在下，MTs的作用与病原体的存活有关，这允许建立感染。阴道毛滴虫是一种原生动物寄生虫，可适应男性泌尿生殖道的微环境，该环境中存在锌（Zn2 +）和镉（Cd2 +）等阳离子。然而，该寄生虫尚未阐明金属耐受性和体内平衡的分子机制。在这项研究中，我们确定了T中有4种潜在的MT样序列（tvmt）。阴道基因组。因为tvmt-2，-3和-4对应于截短的部分基因，所以我们对毛滴虫tvmt-1基因进行了表征。生物信息学分析和预测的蛋白质（TvMT-1）显示出与其他MT报道的相似的特性。分析了在几种二价阳离子（Fe2 +，Mn2 +，Zn2 +和Cd2 +）存在下tvmt-1的表达模式，我们证明了Cd2 +可以显着诱导其表达。通过间接免疫荧光分析，我们证实了在Cd2 +存在下生长的寄生虫细胞质中TvMT-1的这种阳性调节。tvmt-1启动子包含推定的金属响应元件，可能是该基因的Cd2 +依赖性表达的原因。