Crystal structure of glutamate dehydrogenase from the hyperthermophilic eubacterium Thermotoga maritima at 3.0 angstrom resolution
Crystal structure of glutamate dehydrogenase from the hyperthermophilic eubacterium Thermotoga maritima at 3.0 angstrom resolution
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DOI：
10.1006/jmbi.1996.0900
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发表时间：
1997-04-11
影响因子：
5.6
通讯作者：
Ladenstein, R
中科院分区：
文献类型：
--
作者：
Knapp, S;deVos, WM;Ladenstein, R
从极端嗜热菌海栖热袍菌（Thermotoga maritima）中获得了一种极端热稳定的谷氨酸脱氢酶，并通过X射线衍射方法测定了其三维结构。在3%聚乙二醇、120 mM乙酸铵和50 mM bis-tris丙烷（pH 6.5）中生长了最大尺寸为1.2 mm的晶体。晶体属三角晶系，空间群P3（1）21，晶胞尺寸a = B = 147.3埃，c = 273.6埃。这些晶体的衍射极限为3.0埃。测量的衍射数据具有高达3.0埃的分辨率的94%的完整性，并且包含在3.1和3.0埃之间的最后分辨率壳层中的所有可能数据的75%。通过Patterson搜索方法，使用六聚体激烈火球菌谷氨酸脱氢酶作为搜索模型，已经解决了maritima谷氨酸脱氢酶的问题。晶体学精修已经进行到3.1埃的最大分辨率和22.5%的晶体学X值（无R = 29.5%）。T. maritima酶显示六聚体谷氨酸脱氢酶的典型特征：六个亚基以32对称排列。每个亚基由通过柔性铰链区连接的两个结构域组成。二级结构元件以及对酶的催化活性重要的残基是高度保守的。对超嗜热菌T.用来自嗜温细菌共生梭菌（Clostridium symbiosum）的酶对海洋热单胞菌和强烈热单胞菌进行的研究揭示了共同的以及不同的机制有助于这些酶的热稳定性。亚基内离子对的数量增加，亚基内空腔的体积减少，在两种热稳定酶，而显着的差异已被观察到的亚基接口。在P. furiosus谷氨酸脱氢酶中，亚基相互作用主要由大盐桥网络实现的离子相互作用主导。然而，在T.海生物谷氨酸脱氢酶亚基间离子对的数量减少，疏水相互作用增加。(C)出版社：Academic Press Limited。
The extremely thermostable glutamate dehydrogenase from the hyperthermophilic bacterium Thermotoga maritima has been crystallized and the three-dimensional structure has been determined by X-ray diffraction methods. Crystals up to a maximum size of 1.2 mm have been grown in 3% polyethylene glycol, 120 mM ammonium acetate and 50 mM bis-tris propane (pH 6.5). The enzyme crystallized in the trigonal space group P3(1)21 with the cell dimensions a = b = 147.3 Angstrom, c = 273.6 Angstrom. The diffraction limit of these crystals is 3.0 Angstrom. Measured diffraction data have a completeness of 94% up to a resolution of 3.0 Angstrom and contain 75% of all possible data in the last resolution shell between 3.1 and 3.0 Angstrom.The crystal structure of T. maritima glutamate dehydrogenase has been solved by Patterson search methods using the hexameric Pyrococcus furiosus glutamate dehydrogenase as a search model. The crystallographic refinement has been carried out to a maximum resolution of 3.1 Angstrom and an crystallographic X-value of 22.5% (R-free = 29.5% ). The three-dimensional structure of the T. maritima enzyme shows typical features of hexameric glutamate dehydrogenases: six subunits are arranged in 32 symmetry. Each subunit consists of two domains connected by a flexible hinge region. Secondary structure elements as well as residues important for the catalytic activity of the enzyme are highly conserved. A structural comparison of the two glutamate dehydrogenases from the hyperthermophiles T. maritima and P. furiosus with the enzyme from the mesophilic bacterium Clostridium symbiosum has revealed that common as well as distinct mechanisms contribute to the thermal stability of these enzymes. The number of intrasubunit ion pairs is increased and the volume of intrasubunit cavities decreased in both thermostable enzymes, whereas striking differences have been observed in the subunit interfaces. In P. furiosus glutamate dehydrogenase the subunit interactions are dominated by ionic interactions realized by large saltbridge networks. However, in T. maritima glutamate dehydrogenase the number of intersubunit ion pairs is reduced and the hydrophobic interactions are increased. (C) 1997 Academic Press Limited.