Zinc- and iron-rubredoxins from Clostridium pasteurianum at atomic resolution: A high-precision model of a ZnS4 coordination unit in a protein
Zinc- and iron-rubredoxins from Clostridium pasteurianum at atomic resolution: A high-precision model of a ZnS4 coordination unit in a protein
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DOI：
10.1073/pnas.93.17.8836
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发表时间：
1996-08-20
影响因子：
11.1
通讯作者：
Meyer, J
中科院分区：
文献类型：
--
作者：
Dauter, Z;Wilson, KS;Meyer, J
Zn（S-cys）（4）单元存在于许多蛋白质中，其中它承担结构、调节或催化作用，在红蛋白中的铁周围天然地发现相同的配位，其几种结构已经在1埃或接近1埃的分辨率下被精制。小蛋白rubredoxin围绕其金属离子的折叠是许多锌指蛋白的良好模型，锌取代的rubredoxin和其含铁的对应物都是来自巴氏梭菌的rubredoxin编码基因在大肠杆菌中表达的产物。这两种蛋白质的结构已经用原子分辨率的各向异性模型进行了改进（1.1%埃= 8.3%的铁-红氧还蛋白，和1.2埃，R = 9.6%的锌-红氧还蛋白）和非常相似，最显著的差异是增加的长度的M-S键在锌-红氧还蛋白（平均长度，2.345埃）与铁红蛋白相比CA-CB-SG-M二面角的增加涉及Cys-6和Cys-39，Cys-Xaa-Xaa-Cys金属结合基序中的每一个的第一个半胱氨酸，铁被锌取代的另一个结果是，残基36-46周围的区域比多肽链的其余部分经历更大的位移。尽管有这些变化，FeS 4位点的主要特征，即局部2重对称性和N-H键的特征性网络，仍然存在。Zn取代的红氧还蛋白提供了蛋白质中Zn（S-cys）（4）单元的第一个精确结构。围绕铁或锌的红氧还蛋白几乎相同的折叠表明，至少在金属主要具有结构作用的一些位点，例如，锌指-相关金属的选择可由其细胞可用性和动员过程而不是由其化学性质来指导。
The Zn(S-cys)(4) unit is present in numerous proteins, where it assumes structural, regulatory, or catalytic roles, The same coordination is found naturally around iron in rubredoxins, several structures of which have been refined at resolutions of, or near to, 1 Angstrom. The fold of the small protein rubredoxin around its metal ion is an excellent model for many zinc finger proteins, Zn-substituted rubredoxin and its Fe-containing counterpart were both obtained as the products of the expression in Escherichia coli of the rubredoxin-encoding gene from Clostridium pasteurianum. The structures of both proteins have been refined with an anisotropic model at atomic resolution (1.1% Angstrom = 8.3% for Fe-rubredoxin, and 1.2 Angstrom, R = 9.6% for Zn-rubredoxin) and are very similar, The most significant differences are increased lengths pf the M-S bonds in Zn-rubredoxin (average length, 2.345 Angstrom) as compared with Fe-rubredoxin (average length, 2.262 Angstrom), An increase of the CA-CB-SG-M dihedral angles involving Cys-6 and Cys-39, the first cysteines of each of the Cys-Xaa-Xaa-Cys metal binding motifs, has been observed, Another consequence of the replacement of iron by zinc is that the region around residues 36-46 undergoes larger displacements than the remainder of the polypeptide chain, Despite these changes, the main features of the FeS4 site, namely a local 2-fold symmetry and the characteristic network of N-H...S hydrogen bonds, are conserved in the ZnS4 site, The Zn-substituted rubredoxin provides the first precise structure of a Zn(S-cys)(4) unit in a protein, The nearly identical fold of rubredoxin around iron or zinc suggests that at least in some of the sites where the metal has mainly a structural role-e.g., zinc fingers-the choice of the relevant metal may be directed by its cellular availability and mobilization processes rather than by its chemical nature.