Effect of ligand binding on the flexibility of dihydrofolate reductase as revealed by compressibility
Effect of ligand binding on the flexibility of dihydrofolate reductase as revealed by compressibility
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DOI：
10.1016/s0167-4838(00)00019-4
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发表时间：
2000-05-23
期刊：
影响因子：
--
通讯作者：
Gekko, K
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文献类型：
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作者：
Kamiyama, T;Gekko, K
The partial specific volume, nu, and adiabatic compressibility, beta(s), of Escherichia coli dihydrofolate reductase were measured at 30 degrees C in the presence of various ligands (folate, dihydrofolate, tetrahydrofolate, NADPH, NADP, methotrexate, and KCI). Binding of these ligands (binary and ternary complexes) brought about large changes of nu (0.734-0.754 cm(3) g(-1)) and beta(s) (6.6 x 10(-6)-9.8 x 10(-6) bar(-1)), keeping a linear relationship between the two parameters. The values of nu and beta(s) increased with an increase in internal cavity, V-cav, and a decrease in accessible surface area, ASA, which were calculated from the X-ray crystal structures of the complexes. A large variation of V-cav relative to ASA by ligand binding suggested that the cavity is a dominant factor and the effect of hydration might be small for the ligand-induced changes of nu and beta(s). The beta(s) values of the binary and ternary complexes suggested a characteristic conformational flexibility of the kinetic intermediates in the enzyme reaction coordinate. Comparison of beta(s) with the cavity distribution in the crystal structures revealed that the flexibility of the intermediates was mainly determined by the total cavity volume with minor contributions of the number, position, and size of cavities. These results demonstrate that the compressibility is a useful measure of the conformational flexibility of the intermediates in the enzyme reaction and that the combined study of compressibility and X-ray crystallography gives new insight into the protein dynamics through the behavior of the cavities. (C) 2000 Elsevier Science B.V. All rights reserved.
