CRYSTAL-STRUCTURE OF THIOREDOXIN FROM ESCHERICHIA-COLI AT 1.68A RESOLUTION
CRYSTAL-STRUCTURE OF THIOREDOXIN FROM ESCHERICHIA-COLI AT 1.68A RESOLUTION
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DOI：
10.1016/0022-2836(90)90313-b
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发表时间：
1990-03-05
影响因子：
5.6
通讯作者：
EKLUND, H
中科院分区：
文献类型：
--
作者：
KATTI, SK;LEMASTER, DM;EKLUND, H
来自大肠杆菌的硫氧还蛋白的晶体结构已经通过立体化学限制的最小二乘方法精制到在1.68埃时晶体学R因子为0.165。分辨率在最终的模型中，键距与理想值的均方根偏差为0.015埃。并且对于角距离0.035埃。该结构包含来自两个独立分子的1644个蛋白质原子，两个Cu 2+，140个水分子和七个甲基戊二醇分子。在两种替代确认中对10种残留物进行了建模。E.大肠杆菌硫氧还蛋白是一种紧凑的分子，其90%的残基为螺旋，β-股线或反向转弯。该分子由两个构象结构域β组成。阿尔法beta..阿尔法β的和. beta.. beta..α，由单匝α-螺旋和310螺旋。β-片层形成了分子的核心，两侧由疏水残基簇包裹。螺旋形成外表面。Cys 32和Cys 35之间的活性位点二硫桥位于第二α-氨基端。螺旋。由于螺旋偶极子的正静电场可能是重要的稳定过程中的二硫键还原酶功能的蛋白质的阴离子中间体。更具反应性的半胱氨酸Cys 32使其硫原子暴露于溶剂，并且还参与与骨架酰胺基团的氢键。残基29至37包括活性位点半胱氨酸残基，在蛋白质表面上形成突起，并与结构的其余部分产生相对较少的相互作用。二硫桥呈现出扭转角为81 °的右手构象。72度。关于两个分子中的S-S键25对水分子服从非晶体学对称性。它们中的大多数参与建立蛋白质原子之间的分子内氢键相互作用，因此作为折叠蛋白质结构的组成部分而存在。甲基戊二醇分子通常紧靠环并稳定其结构。用于结晶的Cu ~（2+）呈现畸变的八面体正方双锥配位，并在晶体中提供必要的堆积相互作用。这两个独立的蛋白质分子在确认上非常相似，但在原子细节上明显不同（均方根= 0.94埃）。这些差异可能与晶体接触有关，主要集中在远离活性位点的区域。
The crystal structure of thioredoxin from Escherichia coli has been refined by the sterochemically restrained least-squares procedure to a crystallographic R-factor of 0.165 at 1.68 .ANG. resolution. In the final model, the root-mean-square deviation from ideality for bond distances is 0.015 .ANG. and for angle distances 0.035 .ANG.. The structure contains 1644 protein atoms from two independent molecules, two Cu2+, 140 water molecules and seven methylpentanediol molecules. Ten residues have been modeled in two alternative confirmations. E. coli thioredoxin is a compact molecule with 90% of its residues in helices, .beta.-strands or reverse turns. The molecule consists of two conformational domains, .beta..alpha..beta..alpha..beta. and .beta..beta..alpha., connected by a single-turn .alpha.-helix and a 310 helix. The .beta.-sheet forms the core of the molecule packed on either side by cluster of hydrophobic residues. Helices form the external surface. The active site disulfide bridge between Cys32 and Cys35 is located at the amino terminus of the second .alpha.-helix. The positive electrostatic field due to the helical dipole is probably important for stabilizing the anionic intermediate during the disulfide reductase function of the protein. The more reactive cysteine, Cys32, has its sulfur atom exposed to solvent and also involved in a hydrogen bond with a backbone amide group. Residues 29 to 37, which include the active site cysteine residues, form a protrusion on the surface of the protein and make relatively fewer interactions with the rest of the structure. The disulfide bridge exhibits a right-handed conformation with a torsion angle of 81.degree. and 72.degree. about the S-S bond in the two molecules. Twenty-five pairs of water molecules obey the non-crystallographic symmetry. Most of them are involved in establishing intramolecular hydrogen-bonding interactions between protein atoms and thus surve as integral parts of the folded protein structure. Methylpentanediol molecules often pack against the loops and stabilize their structure. Cu2+ used for crysallization exhibit a distorted octahedral square bipyramid co-ordination and provide essential packing interactions in the crystal. The two independent protein molecules are very similar in confirmation but distinctly different in atomic detail (root-mean-square = 0.94 .ANG.). The differences, which may be related to the crystal contacts, are localized mostly to regions far from the active site.