解决方案结构δ5-3-ketosteroid异构酶包裹着类固醇19-nortestosterone hemisuccinate。
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Massiah马,Abeygunawardana C, Gittis AG) Mildvan
解决方案结构δ5-3-ketosteroid异构酶包裹着类固醇19-nortestosterone hemisuccinate。
生物化学。1998年10月20日,37(42):14701 - 12所示。
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9778345 (在PubMed]
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的解决方案结构甾酮异构酶为包裹着产品模拟19-nortestosterone hemisuccinate (19-NTHS)解决了杂环的多维NMR方法使用1647距离限制,77年反角(φ)限制,和67年氢键限制每单体。每个亚基的精炼二级结构包括三个阿尔法螺旋、八beta-strands,四转,两个beta-bulges。beta-strands混合β褶板形式。五的脯氨酸残基,Pro-39独联体,开始模。15第三/四元结构的自洽合奏的酶dimer-steroid复杂,没有违反距离大于0.35,生成了模拟退火和能量最小化程序X-PLOR。二级结构元素的平均成对RMSD是0.63的平均1.25单元和二聚体。在每个单元内,三个阿尔法螺旋装在凹表面的β褶板槽之间的类固醇结合在一个网站定义为14分子间的距离。Tyr-14在生产复杂,从阿尔法螺旋方法asp - 99和3-keto 19-NTHS集团的同时,从beta-strand Asp-38方法的羧酸盐的beta-face类固醇C4和C6附近之间它在催化质子转移。因此isomerase-steroid复杂的解决方案结构可以容纳的催化二分体机制asp - 99捐赠一个氢键Tyr-14反过来是氢连着的3-oxygen类固醇。而直接氢键asp - 99类固醇氧气不太可能,它不能被排除在外。 All other interactions of the steroid with the enzyme are hydrophobic. The dimer interface, which is between the convex surfaces of the beta-sheets, is defined by 28 intersubunit NOEs between hydrophobic residues in the 13C-filtered NOESY-HSQC spectrum of a 13C/12C-heterolabeled dimer. Both hydrophobic and polar interactions occur at the dimer interface which contains no space that would permit additional steroid binding. Comparison of the complexed enzyme with the solution structure of the free enzyme [Wu et al. (1997) Science 276, 415-418] reveals that the three helices change position in the steroid complex, becoming more closely packed onto the concave surface of the beta-sheet, thus bringing Tyr-14 closer to Asp-99 and the substrate. Comparison of the enzyme-steroid complex in solution with the free enzyme in the crystalline state reveals similar differences between the positions of the helices.