Miller M, Rao J K, Wlodawer A, Gribskov M R
Macromolecular Structure Laboratory, NCI-FCRDC, Frederick, MD 21702.
FEBS Lett. 1993 Aug 16;328(3):275-9. doi: 10.1016/0014-5793(93)80943-o.
The crystal structure of L-asparaginase from Erwinia chrysanthemi in the presence and absence of L-aspartate was determined at 1.8 A resolution. Conserved residues in a left-handed crossover (a rare occurrence in protein structures) link pairs of dimers into the catalytically active tetrameric form of the enzyme. The structure of ErA containing bound aspartic acid shows that this unusual strand connectivity is an essential part of the active site architecture, responsible for releasing the product of the enzymatic hydrolysis. The orientation of the bound aspartate indicates for the first time a threonine residue as a catalytic nucleophile.
在有和没有L-天冬氨酸存在的情况下，分别以1.8埃的分辨率测定了来自菊欧文氏菌的L-天冬酰胺酶的晶体结构。左手交叉结构（在蛋白质结构中很少见）中的保守残基将二聚体对连接成酶的催化活性四聚体形式。含有结合天冬氨酸的ErA结构表明，这种不寻常的链连接性是活性位点结构的重要组成部分，负责释放酶促水解产物。结合的天冬氨酸的取向首次表明苏氨酸残基是催化亲核试剂。
