Protein glycosylation regulates many cellular processes. Numerous glycosyltransferases with broad substrate specificities have been structurally characterized. A novel inverting glycosyltransferase, EarP, specifically transfers rhamnose from dTDP-β-l-rhamnose to Arg32 of bacterial translation elongation factor P (EF-P) to activate its function. Here we report a crystallographic study of Neisseria meningitidis EarP. The EarP structure contains two tandem Rossmann-fold domains, which classifies EarP in glycosyltransferase superfamily B. In contrast to other structurally characterized protein glycosyltransferases, EarP binds the entire β-sheet structure of EF-P domain I through numerous interactions that specifically recognize its conserved residues. Thus Arg32 is properly located at the active site, and causes structural change in a conserved dTDP-β-l-rhamnose-binding loop of EarP. Rhamnosylation by EarP should occur via an S_N2 reaction, with Asp20 as the general base. The Arg32 binding and accompanying structural change of EarP may induce a change in the rhamnose-ring conformation suitable for the reaction.

蛋白质糖基化调节许多细胞过程。具有广泛的底物特异性的许多糖基转移酶已经在结构上得到了表征。一种新颖的转化糖基转移酶EarP，将鼠李糖从dTDP-β- 1-鼠李糖转移到细菌翻译延伸因子P（EF-P）的Arg32中，以激活其功能。在这里我们报告脑膜炎奈瑟氏球菌的晶体学研究EarP。EarP结构包含两个串联的Rossmann折叠结构域，该结构将EarP归类为糖基转移酶超家族B。与其他结构特征蛋白糖基转移酶相反，EarP通过多种相互作用结合EF-P结构域I的整个β-折叠结构，这些相互作用专门识别了它的保守结构。残留物。因此，Arg32适当地位于活性位点，并在EarP的保守的dTDP-β- 1-鼠李糖结合环中引起结构改变。EarP的鼠李糖基化应该通过S _N 2反应进行，其中Asp20为一般碱基。EarP的Arg32结合和随之而来的结构变化可能会诱导适合该反应的鼠李糖环构象发生变化。