Bertrand J A, Auger G, Martin L, Fanchon E, Blanot D, Le Beller D, van Heijenoort J, Dideberg O
Laboratoire de Cristallographie Macromoléculaire, Institut de Biologie Structurale Jean-Pierre Ebel (CEA-CNRS), 41 rue Jules Horowitz, Grenoble Cedex 1, F-38027, France.
J Mol Biol. 1999 Jun 11;289(3):579-90. doi: 10.1006/jmbi.1999.2800.
UDP -N- acetylmuramoyl- L -alanine: D -glutamate (MurD) ligase catalyses the addition of d -glutamate to the nucleotide precursor UDP -N- acetylmuramoyl- L -alanine (UMA). The crystal structures of three complexes of Escherichia coli MurD with a variety of substrates and products have been determined to high resolution. These include (1) the quaternary complex of MurD, the substrate UMA, the product ADP, and Mg2+, (2) the quaternary complex of MurD, the substrate UMA, the product ADP, and Mn2+, and (3) the binary complex of MurD with the product UDP - N- acetylmuramoyl- L -alanine- D -glutamate (UMAG). The reaction mechanism supported by these structures proceeds by the phosphorylation of the C-terminal carboxylate group of UMA by the gamma-phosphate group of ATP to form an acyl-phosphate intermediate, followed by the nucleophilic attack by the amino group of D-glutamate to produce UMAG. A key feature in the reaction intermediate is the presence of two magnesium ions bridging negatively charged groups.
UDP-N-乙酰胞壁酰-L-丙氨酸：D-谷氨酸（MurD）连接酶催化将D-谷氨酸添加到核苷酸前体UDP-N-乙酰胞壁酰-L-丙氨酸（UMA）上。已确定了大肠杆菌MurD与多种底物和产物的三种复合物的高分辨率晶体结构。这些包括：（1）MurD、底物UMA、产物ADP和Mg2+的四元复合物；（2）MurD、底物UMA、产物ADP和Mn2+的四元复合物；（3）MurD与产物UDP-N-乙酰胞壁酰-L-丙氨酸-D-谷氨酸（UMAG）的二元复合物。这些结构支持的反应机制是通过ATP的γ-磷酸基团将UMA的C末端羧基磷酸化形成酰基磷酸中间体，随后D-谷氨酸的氨基进行亲核攻击以产生UMAG。反应中间体的一个关键特征是存在两个桥接带负电荷基团的镁离子。
