In Trichomonas vaginalis, the TvCyP1-catalyzed conformational switches of two glycinyl-prolyl imide bonds in Myb3 were previously shown to regulate the trafficking of Myb3 from cytoplasmic membrane compartments towards the nucleus. In this study, TvCyP2 was identified as a second cyclophilin that binds to Myb3 at the same dipeptide motifs. The enzymatic proficiency of TvCyP2, but not its binding to Myb3, was aborted by a mutation of Arg75 in the catalytic domain. TvCyP2 was localized to the endoplasmic reticulum with a weak signal that extensively extends into the cytoplasm as well as to the plasma membrane according to an immunofluorescence assay. Moreover, TvCyP2 was co-enriched with TvCyP1 and Myb3 in various membrane fractions purified by differential and gradient centrifugation. TvCyP2 was found to proficiently enzymatically regulate the distribution of TvCyP1 and Myb3 among purified membrane fractions, and to localize TvCyP1 in hydrogenosomes and on plasma membranes. Protein complexes immunoprecipitated from lysates of cells overexpressing TvCyP1 and TvCyP2 were found to share some common components, like TvCyP1, TvCyP2, TvBip, Myb3, TvHSP72, and the hydrogenosomal heat shock protein 70 (HSP70). Direct interaction between TvCyP1 and TvCyP2 was confirmed by a GST pull-down assay. Fusion of vesicles with hydrogenosomes was observed by transmission electron microscopy, whereas TvCyP1, TvCyP2, and Myb3 were each detected at the fusion junction by immunoelectron microscopy. These observations suggest that T. vaginalis may have evolved a novel protein trafficking pathway to deliver proteins among the endomembrane compartments, hydrogenosomes and plasma membranes.

中文翻译：

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内膜蛋白运输受原生动物寄生虫阴道毛滴虫中TvCyP2亲环蛋白的调节。

在阴道毛滴虫中，先前已显示Myb3中TvCyP1催化的两个甘氨酰-脯氨酰胺键的构象转换调节Myb3从细胞质膜区室向细胞核的运输。在这项研究中，TvCyP2被鉴定为第二个亲环素，以相同的二肽基序与Myb3结合。TvCyP2的酶促能力（但未与Myb3结合）却由于催化域中Arg75的突变而中止。根据免疫荧光测定，TvCyP2定位于内质网，信号较弱，可广泛延伸到细胞质以及质膜。此外，TvCyP2与TvCyP1和Myb3共富集了通过差速和梯度离心纯化的各种膜级分。TvCyP2被发现可以有效地酶促调节TvCyP1和Myb3在纯化的膜级分之间的分布，并且可以将TvCyP1定位在氢体和质膜上。从过表达TvCyP1和TvCyP2的细胞裂解物中免疫沉淀的蛋白质复合物被发现具有一些共同的成分，如TvCyP1，TvCyP2，TvBip，Myb3，TvHSP72和氢染色体热休克蛋白70（HSP70）。TvCyP1和TvCyP2之间的直接相互作用通过GST下拉测定法得以证实。通过透射电子显微镜观察到囊泡与氢核小体融合，而通过免疫电子显微镜在融合连接处分别检测到TvCyP1，TvCyP2和Myb3。这些观察结果表明，阴道锥虫可能已经进化出一种新的蛋白质运输途径，可以在内膜区室之间传递蛋白质，