Wilmanns M, Priestle J P, Niermann T, Jansonius J N
Department of Structural Biology, University of Basel, Switzerland.
J Mol Biol. 1992 Jan 20;223(2):477-507. doi: 10.1016/0022-2836(92)90665-7.
The three-dimensional structure of the monomeric bifunctional enzyme N-(5'-phosphoribosyl)anthranilate isomerase:indole-3-glycerol-phosphate synthase from Escherichia coli has been refined at 2.0 A resolution, using oscillation film data obtained from synchrotron radiation. The model includes the complete protein (452 residues), two phosphate ions and 628 water molecules. The final R-factor is 17.3% for all observed data between 15 and 2 A resolution. The root-mean-square deviations from ideal bond lengths and bond angles are 0.010 A and 3.2 degrees, respectively. The structure of N-(5'-phosphoribosyl)anthranilate isomerase: indole-3-glycerol-phosphate synthase from E. coli comprises two beta/alpha-barrel domains that superimpose with a root-mean-square deviation of 2.03 A for 138 C alpha-pairs. The C-terminal domain (residues 256 to 452) catalyses the PRAI reaction and the N-terminal domain (residues 1 to 255) catalyses the IGPS reaction, two sequential steps in tryptophan biosynthesis. The enzyme has the overall shape of a dumb-bell, resulting in a surface area that is considerably larger than normally observed for monomeric proteins of this size. The active sites of the PRAI and the IGPS domains, both located at the C-terminal side of the central beta-barrel, contain equivalent binding sites for the phosphate moieties of the substrates N-(5'-phosphoribosyl) anthranilate and 1-(o-carboxyphenylamino)-1-deoxyribulose-5-phosphate. These two phosphate binding sites are identical with respect to their positions within the tertiary structure of the beta/alpha-barrel, the conformation of the residues involved in phosphate binding and the hydrogen-bonding network between the phosphate ions and the protein. The active site cavities of both domains contain similar hydrophobic pockets that presumably bind the anthranilic acid moieties of the substrates. These similarities of the tertiary structures and the active sites of the two domains provide evidence that N-(5'-phosphoribosyl)anthranilate isomerase:indole-3-glycerol-phosphate synthase from E. coli results from a gene duplication event of a monomeric beta/alpha-barrel ancestor.
来自大肠杆菌的单体双功能酶N -（5'-磷酸核糖基）邻氨基苯甲酸异构酶：吲哚-3-甘油磷酸合酶的三维结构已利用从同步辐射获得的振荡胶片数据在2.0埃分辨率下进行了精修。该模型包括完整的蛋白质（452个残基）、两个磷酸根离子和628个水分子。对于15至2埃分辨率之间的所有观测数据，最终的R因子为17.3%。与理想键长和键角的均方根偏差分别为0.010埃和3.2度。来自大肠杆菌的N -（5'-磷酸核糖基）邻氨基苯甲酸异构酶：吲哚-3-甘油磷酸合酶的结构由两个β/α-桶状结构域组成，对于138个Cα对，它们的叠加均方根偏差为2.03埃。C末端结构域（残基256至452）催化PRAI反应，N末端结构域（残基1至255）催化IGPS反应，这是色氨酸生物合成中的两个连续步骤。该酶整体呈哑铃状，导致其表面积比这种大小的单体蛋白通常观察到的要大得多。PRAI和IGPS结构域的活性位点均位于中央β-桶的C末端一侧，包含底物N -（5'-磷酸核糖基）邻氨基苯甲酸和1-（邻羧基苯基氨基）-1-脱氧核糖-5-磷酸的磷酸部分的等效结合位点。这两个磷酸结合位点在β/α-桶的三级结构中的位置、参与磷酸结合的残基构象以及磷酸根离子与蛋白质之间的氢键网络方面是相同的。两个结构域的活性位点腔都包含类似的疏水口袋，推测这些口袋结合底物的邻氨基苯甲酸部分。这两个结构域的三级结构和活性位点的这些相似性提供了证据，表明来自大肠杆菌的N -（5'-磷酸核糖基）邻氨基苯甲酸异构酶：吲哚-3-甘油磷酸合酶是由单体β/α-桶祖先的基因复制事件产生的。
