Abstract：
Neryl diphosphate (C10) synthase (NDPS1), a homodimeric soluble cis-prenyltransferase from tomato, contains four disulfide bonds, including two inter-subunit S-S bonds in the N-terminal region. Mutagenesis studies demonstrated that the S-S bond formation affects not only the stability of the dimer but also the catalytic efficiency of NDPS1. Structural polymorphs in the crystal structures of NDPS1 complexed with its substrate and substrate analog were identified by employing massive data collections and hierarchical clustering analysis. Heterogeneity of the C-terminal region, including the conserved RXG motifs, was observed in addition to the polymorphs of the binding mode of the ligands. One of the RXG motifs covers the active site with an elongated random coil when the ligands are well-ordered. Conversely, the other RXG motif was located away from the active site with a helical structure. The heterogeneous C-terminal regions suggest alternating structural transitions of the RXG motifs that result in closed and open states of the active sites. Site-directed mutagenesis studies demonstrated that the conserved glycine residue cannot be replaced. We propose that the putative structural transitions of the order/disorder of N-terminal regions and the closed/open states of C-terminal regions may cooperate and be important for the catalytic mechanism of NDPS1.
摘要：
橙酰二磷酸（C10）合成酶（NDPS1），来自番茄的同二聚体可溶性顺式-异戊二烯基转移酶，含有四个二硫键，在N末端区域中包括两个亚基间S-S键。诱变研究表明，S-S键的形成不仅影响二聚体的稳定性，而且影响NDPS1的催化效率。通过采用大量数据收集和层次聚类分析，鉴定了NDPS1与其底物和底物类似物复合的晶体结构中的结构多晶型物。C端区域的异质性，包括保守的RXG图案，除了配体的结合模式的多晶型物外，还观察到。当配体是有序的时,RXG基序之一用细长的无规卷曲覆盖活性位点。相反，另一个RXG基序位于远离具有螺旋结构的活性位点的位置。异质C末端区域表明RXG基序的交替结构转变，导致活性位点的封闭和开放状态。定点诱变研究表明保守的甘氨酸残基不能被替换。我们建议N末端区域的有序/无序和C末端区域的封闭/开放状态的推定结构转变可能会合作，并且对于NDPS1的催化机理很重要。
