Roderick S L, Matthews B W
Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene 97403.
Biochemistry. 1993 Apr 20;32(15):3907-12. doi: 10.1021/bi00066a009.
The X-ray structure of Escherichia coli methionine aminopeptidase (MAP) has been determined to 2.4-A resolution and refined to a crystallographic R-factor of 18.2%. The fold is novel and displays internal pseudo-2-fold symmetry which structurally relates the first and second halves of the polypeptide chain. The topology consists of a central antiparallel beta-sheet covered on one side by two pairs of alpha-helices and by a C-terminal loop. The other face of the beta-sheet, together with some irregular loops, forms the active site, which contains two cobalt ions 2.9 A apart. These metal ions are liganded by the side chains of Asp 97, Asp 108, Glu 204, Glu 235, and His 171 with approximate octahedral coordination. In terms of both the novel backbone fold and the constitution of the active site, MAP appears to represent a new class of proteolytic enzyme.
大肠杆菌甲硫氨酸氨肽酶（MAP）的X射线结构已确定至2.4埃分辨率，并精修至晶体学R因子为18.2%。其折叠方式新颖，呈现内部伪二重对称，在结构上关联了多肽链的前半段和后半段。拓扑结构由一个中央反平行β折叠组成，一侧被两对α螺旋和一个C末端环覆盖。β折叠的另一面，连同一些不规则环，形成了活性位点，其中包含两个相距2.9埃的钴离子。这些金属离子由天冬氨酸97、天冬氨酸108、谷氨酸204、谷氨酸235和组氨酸171的侧链以近似八面体配位方式配位。就新颖的主链折叠和活性位点的组成而言，MAP似乎代表了一类新的蛋白水解酶。
