The 2.1-A resolution structure of iron superoxide dismutase from Pseudomonas ovalis.
The 2.1-A resolution structure of iron superoxide dismutase from Pseudomonas ovalis.
复制标题
来自卵形假单胞菌的铁超氧化物歧化酶的 2.1-A 解析结构。
作者：
Barry L. Stoddard;P. Lynne Howell;Dagmar Ringe;G. Petsko
对来自卵形假单胞菌的天然未络合的铁超氧化物歧化酶（EC 1.15.1.1）的2.1-A分辨率晶体结构进行解析并精制至最终R因子为24%。二聚体结构中每个单体含有一个催化铁中心，蛋白质配体与金属的不对称三角双锥配位。每个单体含有两个结构域，三角形配体（组氨酸74和160;天冬氨酸156）由大结构域贡献，并通过扩展的氢键网络稳定，包括来自相对单体的残基。轴向配体（组氨酸26）被发现的小域，并没有广泛参与稳定的H-键网络。铁的开放轴向配位位置没有结合水分子或阴离子。该金属位于三角形配体平面外朝向组氨酸26的0.5 A处，提供远离铁结合位点的略微偏斜的配位。该分子在活性位点中含有谷氨酰胺残基，该残基在测序数据的所有铁酶之间是保守的，但在序列中单独位置的所有锰SOD之间是保守的。该残留物在这两种情况下显示出相同的结构相互作用，这意味着铁和锰SOD是彼此的第二位点回复突变体。
The 2.1-A resolution crystal structure of native uncomplexed iron superoxide dismutase (EC 1.15.1.1) from Pseudomonas ovalis was solved and refined to a final R factor of 24%. The dimeric structure contains one catalytic iron center per monomer with an asymmetric trigonal-bipyramidal coordination of protein ligands to the metal. Each monomer contains two domains, with the trigonal ligands (histidines 74 and 160; aspartate 156) contributed by the large domain and stabilized by an extended hydrogen-bonded network, including residues from opposing monomers. The axial ligand (histidine 26) is found on the small domain and does not participate extensively in the stabilizing H-bond network. The open axial coordination position of the iron is devoid of bound water molecules or anions. The metal is located 0.5 A out of the plane of the trigonal ligands toward histidine 26, providing a slightly skewed coordination away from the iron binding site. The molecule contains a glutamine residue in the active site which is conserved between all iron enzymes sequenced to data but which is conserved among all manganese SODs at a separate position in the sequence. This residue shows the same structural interactions in both cases, implying that iron and manganese SODs are second-site revertants of one another.