Interactions of a novel inhibitor from an extremophilic <i>Bacillus</i> sp with HIV-1 protease -: Implications for the mechanism of inactivation

作     者：Dash, C Rao, M 

作者机构：Natl Chem Lab Div Biochem Sci Pune 411008 Maharashtra India 

出 版 物：《JOURNAL OF BIOLOGICAL CHEMISTRY》 (生物化学杂志)

年 卷 期：2001年第276卷第4期

页      面：2487-2493页

核心收录：

学科分类：0710[理学-生物学] 071010[理学-生物化学与分子生物学] 07[理学] 

主　　题：氨基酸序列 芽孢杆菌属 细菌蛋白质类/化学 细菌蛋白质类/药理学 HIV蛋白酶/药物作用 HIV蛋白酶抑制药/化学 HIV蛋白酶抑制药/药理学 HIV-1/酶学 质谱分析法 模型 生物学 模型 分子 寡肽类/化学 寡肽类/药理学 蛋白质结合 蛋白质构象/药物作用 蛋白质结构 二级 序列分析 蛋白质 

摘      要：The active site cleft of the HIV-1 protease (PR) is bound by two identical conformationally mobile loops known as flaps, which are important for substrate binding and catalysis, The present article reports, for the first time, an HIV-1 PR inhibitor, ATBI, from an extremophilic Bacillus sp. The inhibitor is found to be a hydrophilic peptide with Mr of 1147, and an amino acid sequence of Ala-Gly-Lys-Lys-Asp-Asp-Asp-Asp-Pro-Pro-Glu, Sequence homology exhibited no similarity with the reported peptidic inhibitors of HIV-1 PR. Investigation of the kinetics of the enzyme-inhibitor interactions revealed that ATBI is a noncompetitive and tight binding inhibitor with the IC50 and K-i values 18.0 and 17.8 nM, respectively. The binding of the inhibitor with the enzyme and the subsequent induction of the localized conformational changes in the flap region of the HIV-1 PR were monitored by exploiting the intrinsic fluorescence of the surface exposed Trp-42 residues, which are present at the proximity of the flaps. We have demonstrated by fluorescence and circular dichroism studies that ATBI binds in the active site of the HIV-1 PR and thereby leads to the inactivation of the enzyme. Based on our results, we propose that the inactivation is due to the reorganization of the flaps impairing its flexibility leading toward inaccessibility of the substrate to the active site of the enzyme.