THE CRYSTAL-STRUCTURE OF AN ENGINEERED MONOMERIC TRIOSEPHOSPHATE ISOMERASE, MONOTIM - THE CORRECT MODELING OF AN 8-RESIDUE LOOP
THE CRYSTAL-STRUCTURE OF AN ENGINEERED MONOMERIC TRIOSEPHOSPHATE ISOMERASE, MONOTIM - THE CORRECT MODELING OF AN 8-RESIDUE LOOP
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DOI：
10.1016/0969-2126(93)90021-8
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发表时间：
1993-11-15
期刊：
影响因子：
5.7
通讯作者：
WIERENGA, RK
中科院分区：
文献类型：
--
作者：
BORCHERT, TV;ABAGYAN, R;WIERENGA, RK
背景：磷酸三糖异构酶（TIM）折叠存在于几种不同类别的酶中，其中大多数是寡聚物； TIM 本身始终充当非常紧密的二聚体。最近的研究表明，可以通过用 8 个残基片段替换 15 个残基界面环 Loop-3 来构建 TIM 的单体形式（“monoTIM”）；模型表明，这应该会产生一个短的无应变转角，从而产生随后的螺旋，即螺旋-A3，在其氨基末端有一个额外的转角。结果：monoTIM 的晶体结构表明，它保留了特征性的 TIM 桶（β α）8 倍，并且新环的结构与预测的结构非常接近。另外两个界面环 Loop-1 和 Loop-4 分别包含活性位点残基 Lys13 和 His95，与二聚体野生型 TIM 相比，monoTIM 的结构发生了显着变化。 结论：观察到的 monoTIM 和野生型 TIM 之间的结构差异表明，TIM 的二聚体外观决定了四个催化残基中两个的位置和构象。
Background: The triosephosphate isomerase (TIM) fold is found in several different classes of enzymes, most of which are oligomers; TIM itself always functions as a very tight dimer. It has recently been shown that a monomeric form of TIM ('monoTIM') can be constructed by replacing a 15-residue interface loop, loop-3, with an eight-residue fragment; modelling suggests that this should result in a short strain-free turn, resulting in the subsequent helix, helix-A3, having an additional turn at its amino terminus.Results: The crystal structure of monoTIM shows that it retains the characteristic TIM-barrel (beta alpha)8-fold and that the new loop has a structure very close to that predicted. Two other interface loops, loop-1 and loop-4, which contain the active site residues Lys13 and His95, respectively, show significant changes in structure in monoTIM compared with dimeric wild-type TIM.Conclusion: The observed structural differences between monoTIM and wild-type TIM indicate that the dimeric appearance of TIM determines the location and conformation of two of the four catalytic residues.