Structure-Activity Studies of the Inhibition of FabI, the Enoyl Reductase from Escherichia coli, by Triclosan: Kinetic Analysis of Mutant FabIs
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- 作者：Sharada Sivaraman ; Jacque Zwahlen ; Alasdair F. Bell ; Lizbeth Hedstrom ; and Peter J. Tonge
- 刊名：Biochemistry
- 出版年：2003
- 出版时间：April 22, 2003
- 年：2003
- 卷：42
- 期：15
- 页码：4406 - 4413
- 全文大小：145K
- 年卷期：v.42,no.15(April 22, 2003)
- ISSN：1520-4995
文摘
Triclosan, a common antibacterial additive used in consumer products, is an inhibitor of FabI,the enoyl reductase enzyme from type II bacterial fatty acid biosynthesis. In agreement with previousstudies [Ward, W. H., Holdgate, G. A., Rowsell, S., McLean, E. G., Pauptit, R. A., Clayton, E., Nichols,W. W., Colls, J. G., Minshull, C. A., Jude, D. A., Mistry, A., Timms, D., Camble, R., Hales, N. J.,Britton, C. J., and Taylor, I. W. (1999) Biochemistry 38, 12514-12525], we report here that triclosan isa slow, reversible, tight binding inhibitor of the FabI from Escherichia coli. Triclosan binds preferentiallyto the E·NAD+ form of the wild-type enzyme with a K1 value of 23 pM. In agreement with geneticselection experiments [McMurry, L. M., Oethinger, M., and Levy, S. B. (1998) Nature 394, 531-532],the affinity of triclosan for the FabI mutants G93V, M159T, and F203L is substantially reduced, bindingpreferentially to the E·NAD+ forms of G93V, M159T, and F203L with K1 values of 0.2 
M, 4 nM, and0.9 nM, respectively. Triclosan binding to the E·NADH form of F203L can also be detected and is definedby a K2 value of 51 nM. We have also characterized the Y156F and A197M mutants to compare andcontrast the binding of triclosan to InhA, the homologous enoyl reductase from Mycobacterium tuberculosis.As observed for InhA, Y156F FabI has a decreased affinity for triclosan and the inhibitor binds to bothE·NAD+ and E·NADH forms of the enzyme with K1 and K2 values of 3 and 30 nM, respectively. Thereplacement of A197 with Met has no impact on triclosan affinity, indicating that differences in the sequenceof the conserved active site loop cannot explain the 10000-fold difference in affinities of FabI and InhAfor triclosan.
M, 4 nM, and0.9 nM, respectively. Triclosan binding to the E·NADH form of F203L can also be detected and is definedby a K2 value of 51 nM. We have also characterized the Y156F and A197M mutants to compare andcontrast the binding of triclosan to InhA, the homologous enoyl reductase from Mycobacterium tuberculosis.As observed for InhA, Y156F FabI has a decreased affinity for triclosan and the inhibitor binds to bothE·NAD+ and E·NADH forms of the enzyme with K1 and K2 values of 3 and 30 nM, respectively. Thereplacement of A197 with Met has no impact on triclosan affinity, indicating that differences in the sequenceof the conserved active site loop cannot explain the 10000-fold difference in affinities of FabI and InhAfor triclosan.