ENZYME STRUCTURE

多酶复合物，来自鼠伤寒沙门氏菌的色氨酸合成酶， 用X-射线衍射法进行了分析。 新的超高分辨率 已经测量了β亚基的突变体的数据，在外部环境中， 醛亚胺与氨基酸丝氨酸和色氨酸形成，并且这些 结构已经完善。 这一分析提供了新的信息 关于β活性位点中残基的分布及其 与β反应的中间体相互作用。 用X射线衍射分析了根霉胃蛋白酶抑制剂复合物 衍射，以获得更多的信息， 作用机制。 其中一个提供了一个四面体的模型 过渡态的中间体。接触距离检查 这一复杂性为先前提出的建议提供了有力的支持。 作用机制。 本文提出了一种新的X射线和核磁共振联合精化方法 数据这种方法可以证明， 这些结构是由所使用的程序产生的，可以突出真实的 由物理差异引起的构象差异，如晶体 打包

The multi-enzyme complex, tryptophan synthase from salmonella typhimurium, has been further analyzed by X-ray diffraction. New very high resolution data have been measured for a mutant of the beta subunit, in the external aldimine form with the amino acids serine and tryptophan, and these structures have been refined. This analysis provides new information about the disposition of residues in the beta active site and their interaction with the intermediates of the beta reaction. Inhibitor complexes of rhizopus pepsin have been analyzed by X-ray diffraction with a view to obtaining more information concerning the mechanism of action. One of these provides a model for the tetrahedral intermediate of the transition state. Examination of the contact distances of this complex provides strong support for the previously proposed mechanism of action. A new method has been presented for the joint refinement of X-ray and NMR data. This method can demonstrate that only very small differences between the structures result from the procedures used, and can highlight real conformational differences caused by physical differences such as crystal packing.