Zinc environment and cis peptide bonds in carboxypeptidase A at 1.75-A resolution.
Zinc environment and cis peptide bonds in carboxypeptidase A at 1.75-A resolution.
复制标题
羧肽酶 A 中的锌环境和顺式肽键，分辨率为 1.75-A。
DOI：
10.1073/pnas.78.6.3408
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发表时间：
1981
影响因子：
11.1
通讯作者：
Hardman,KD
中科院分区：
文献类型：
--
作者：
Rees,DC;Lewis,M;Honzatko,RB;Lipscomb,WN;Hardman,KD
金属酶羧肽酶A（肽基-L-氨基酸水解酶，EC 3.4.17.1）的结构已通过限制性最小二乘法在1.75 A处被精修至0.162的常规晶体学R因子。精细结构相对于催化机制的显着结果进行了描述。在天然酶中，锌配位数为5（两个咪唑N δ 1氮，两个谷氨酸-72的羧酸氧和一个水分子）。然而，在羧肽酶A与二肽甘氨酰-L-酪氨酸的复合物（在2.0-A分辨率下）中，水配体被二肽的羰基氧和氨基氮取代。氨基氮在统计学上也占据了谷氨酸-270附近的第二个位置。因此，在羧肽酶A-底物复合物中锌的配位数可以从5到6不等。这些结果的影响羧肽酶A的催化机制进行了讨论。此外，三个顺式肽键，其中没有一个涉及脯氨酸作为氨基氮供体，已位于相当接近的活性位点。
The structure of the metalloenzyme carboxypeptidase A (peptidyl-L-amino-acid hydrolase, EC 3.4.17.1) has been refined at 1.75 A by a restrained least-squares procedure to a conventional crystallographic R factor of 0.162. Significant results of the refined structure relative to the catalytic mechanism are described. In the native enzyme, the zinc coordination number is five (two imidazole N delta 1 nitrogens, the two carboxylate oxygens of glutamate-72, and a water molecule). In the complex (at 2.0-A resolution) of carboxypeptidase A with the dipeptide glycyl-L-tyrosine, however, the water ligand is replaced by both the carbonyl oxygen and the amino nitrogen of the dipeptide. The amino nitrogen also statistically occupies a second position near glutamate-270. Consequently, the coordination number of zinc may vary from five to six in carboxypeptidase A-substrate complexes. Implications of these results for the catalytic mechanism of carboxypeptidase A are discussed. In addition, three cis peptide bonds, none of which involves proline as the amino nitrogen donor, have been located fairly near the active site.