Jeffery C J, Barry T, Doonan S, Petsko G A, Ringe D
Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02254-9110, USA.
Protein Sci. 1998 Jun;7(6):1380-7. doi: 10.1002/pro.5560070614.
The crystal structure of Saccharomyces cerevisiae cytoplasmic aspartate aminotransferase (EC 2.6.1.1) has been determined to 2.05 A resolution in the presence of the cofactor pyridoxal-5'-phosphate and the competitive inhibitor maleate. The structure was solved by the method of molecular replacement. The final value of the crystallographic R-factor after refinement was 23.1% with good geometry of the final model. The yeast cytoplasmic enzyme is a homodimer with two identical active sites containing residues from each subunit. It is found in the "closed" conformation with a bound maleate inhibitor in each active site. It shares the same three-dimensional fold and active site residues as the aspartate aminotransferases from Escherichia coli, chicken cytoplasm, and chicken mitochondria, although it shares less than 50% sequence identity with any of them. The availability of four similar enzyme structures from distant regions of the evolutionary tree provides a measure of tolerated changes that can arise during millions of years of evolution.
在辅因子磷酸吡哆醛和竞争性抑制剂马来酸存在的情况下，已将酿酒酵母细胞质天冬氨酸氨基转移酶（EC 2.6.1.1）的晶体结构解析到2.05埃的分辨率。该结构通过分子置换法解析。精修后晶体学R因子的最终值为23.1%，最终模型的几何结构良好。酵母细胞质酶是一种同型二聚体，有两个相同的活性位点，每个亚基都有相应的残基。在每个活性位点都有一个结合的马来酸抑制剂的情况下，它处于“封闭”构象。它与来自大肠杆菌、鸡细胞质和鸡线粒体的天冬氨酸氨基转移酶具有相同的三维折叠和活性位点残基，尽管它与其中任何一种的序列同一性都不到50%。来自进化树不同区域的四种相似酶结构的可得性提供了数百万年进化过程中可能出现的可耐受变化的一种衡量标准。
