In many metazoan species, an unusual type of protein glycosylation, called C-mannosylation, occurs on adhesive thrombospondin type 1 repeats (TSRs) and type I cytokine receptors. This modification has been shown to be catalyzed by the Caenorhabditis elegans DPY-19 protein and orthologues of the encoding gene were found in the genome of apicomplexan parasites. Lately, the micronemal adhesin thrombospondin-related anonymous protein (TRAP) was shown to be C-hexosylated in Plasmodium falciparum sporozoites. Here, we demonstrate that also the micronemal protein MIC2 secreted by Toxoplasma gondii tachyzoites is C-hexosylated. When expressed in a mammalian cell line deficient in C-mannosylation, P. falciparum and T. gondii Dpy19 homologues were able to modify TSR domains of the micronemal adhesins TRAP/MIC2 family involved in parasite motility and invasion. In vitro, the apicomplexan enzymes can transfer mannose to a WXXWXXC peptide but, in contrast to C. elegans or mammalian C-mannosyltransferases, are inactive on a short WXXW peptide. Since TSR domains are commonly found in apicomplexan surface proteins, C-mannosylation may be a common modification in this phylum.

中文翻译：

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蚜复合体C-甘露糖基转移酶修饰TRAP家族的血小板反应蛋白I型粘附素。

在许多后生动物物种中，一种异常的蛋白质糖基化类型称为C-甘露糖基化，发生在粘附性血小板反应蛋白1型重复序列（TSR）和I型细胞因子受体上。已经表明这种修饰是由秀丽隐杆线虫DPY-19蛋白催化的，并且在apiplexplexan寄生虫的基因组中发现了编码基因的直向同源物。最近，微小恶性粘附素血小板反应蛋白相关的匿名蛋白（TRAP）在恶性疟原虫子孢子中被证明是C-己糖基化的。在这里，我们证明了弓形虫速殖子分泌的微神经蛋白MIC2也是C-己糖基化的。当在哺乳动物细胞系中表达不足时C-甘露糖基化，恶性疟原虫和弓形虫Dpy19同源物能够修饰参与寄生虫运动和侵袭的微神经粘附素TRAP / MIC2家族的TSR域。在体外，apicomplexan酶可以将甘露糖转移到WXXWXXC肽上，但是与秀丽隐杆线虫或哺乳动物C-甘露糖基转移酶相反，它对短的WXXW肽没有活性。由于TSR结构域通常存在于apicomplexan表面蛋白中，因此C-甘露糖基化可能是该门中的常见修饰。