STRUCTURE OF THERMOLYSIN - ELECTRON-DENSITY MAP AT 2.3 A RESOLUTION
STRUCTURE OF THERMOLYSIN - ELECTRON-DENSITY MAP AT 2.3 A RESOLUTION
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DOI：
10.1016/0022-2836(72)90569-4
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发表时间：
1972-01-01
影响因子：
5.6
通讯作者：
JANSONIUS, JN
中科院分区：
文献类型：
--
作者：
COLMAN, PM;MATTHEWS, BW;JANSONIUS, JN
测定了耐热蛋白酶嗜热菌蛋白酶的电子密度图，其分辨率为2.3 μ m。晶体学的细节给出了用于结构测定的三个同晶重原子衍生物。多肽链的过程可以通过电子密度图进行跟踪，而无需参考化学测定的氨基酸序列，并且53%的氨基酸被正确鉴定。电子密度图与Titani、Hermodson、Ericsson、沃尔什和Neurath（1972）测定的氨基酸序列相结合，相当详细地揭示了嗜热菌蛋白酶分子的构象。该分子折叠成两个不同的裂片，其中一半是β结构，另一半是螺旋结构。必需的锌原子位于两个裂片之间的深裂中，并有两个组氨酸和一个谷氨酸作为配体，如在羧肽酶A中。活性部位的其他一些元件与羧肽酶A的类似，但也有一些显著的差异。嗜热菌蛋白酶和羧肽酶A的整体结构是完全不同的。结果表明，嗜热菌蛋白酶结合四个钙离子，这可能会在不同程度上取代锶，钡和稀土金属离子。
An electron density map at 2.3 Å resolution has been determined for the thermostable protease thermolysin. Crystallographic details are given for the three isomorphous heavy-atom derivatives which were used in the structure determination. The course of the polypeptide chain could be followed through the electron density map without reference to the chemically determined amino-acid sequence and 53% of the amino acids identified correctly. The electron density map, when combined with the amino-acid sequence determined by Titani, Hermodson, Ericsson, Walsh & Neurath (1972), revealed the conformation of the thermolysin molecule in considerable detail. The molecule is folded into two distinct lobes, with β-structure predominating in one half and helices in the other. The essential zinc atom lies between the two lobes in a deep cleft and has as ligands two histidines and a glutamic acid as in carboxypeptidase A. Some other elements of the active site are similar to that of carboxypeptidase A, but there are also some striking differences. The over-all structures of thermolysin and carboxypeptidase A are quite different. It is shown that thermolysin binds four calcium ions, which may be replaced to varying degrees by ions of strontium, barium and the rare earth metals.