Structural Insights into the Catalytic Mechanism of Bacterial Guanosine-diphospho-D-mannose Pyrophosphorylase and Its Regulation by Divalent Ions
Structural Insights into the Catalytic Mechanism of Bacterial Guanosine-diphospho-D-mannose Pyrophosphorylase and Its Regulation by Divalent Ions
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DOI：
10.1074/jbc.m109.095182
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发表时间：
2010-08-27
影响因子：
4.8
通讯作者：
Bourne, Yves
中科院分区：
文献类型：
--
作者：
Pelissier, Marie-Cecile;Lesley, Scott A.;Bourne, Yves
GMP 催化 GDP-Man 的形成，GDP-Man 是蛋白质糖基化以及细菌细胞壁和荚膜多糖生物合成的基本前体。来自嗜热细菌海栖热袍菌的 GMP 晶体结构以 apo 形式与底物 1-磷酸甘露糖或 GTP 复合，并在必要的二价阳离子 Mg2+ 存在下与最终产物 GDP-Man 结合，在 2.1-2.8 埃的分辨率范围内解析。 T. maritima GMP 分子由两个独立的结构域组成：N 端罗斯曼折叠样结构域和 C 端左手 β 螺旋结构域。两个分子通过 C 端结构域的尾对尾排列结合成二聚体。结构的比较分析以及酶参数的表征揭示了此类糖核苷酸转移酶的底物特异性的基础。特别是，底物和产物的结合与活性中心内衬环区域的构象以及两个结构域的相对方向的显着变化相关。 N 端和 C 端结构域的参与，加上二价金属离子的催化作用，突出了细菌 GMP 与焦磷酸化酶超家族其他成员相比的催化特征。
GMP catalyzes the formation of GDP-Man, a fundamental precursor for protein glycosylation and bacterial cell wall and capsular polysaccharide biosynthesis. Crystal structures of GMP from the thermophilic bacterium Thermotoga maritima in the apo form, in complex with the substrates mannose-1-phosphate or GTP and bound with the end product GDP-Man in the presence of the essential divalent cation Mg2+, were solved in the 2.1-2.8 angstrom resolution range. The T. maritima GMP molecule is organized in two separate domains: a N-terminal Rossman fold-like domain and a C-terminal left-handed beta-helix domain. Two molecules associate into a dimer through a tail-to-tail arrangement of the C-terminal domains. Comparative analysis of the structures along with characterization of enzymatic parameters reveals the bases of substrate specificity of this class of sugar nucleotidyltransferases. In particular, substrate and product binding are associated with significant changes in the conformation of loop regions lining the active center and in the relative orientation of the two domains. Involvement of both the N- and C-terminal domains, coupled to the catalytic role of a bivalent metal ion, highlights the catalytic features of bacterial GMPs compared with other members of the pyrophosphorylase superfamily.