Department of Chemistry, Presidency University, Kolkata 700 073, India.
J Photochem Photobiol B. 2012 Oct 3;115:93-104. doi: 10.1016/j.jphotobiol.2012.07.002. Epub 2012 Jul 17.
The interaction of antibiotic Tetracycline hydrochloride (TC) with Alkaline Phosphatase (AP) from Escherichia coli, an important target enzyme in medicinal chemistry, having tryptophan (Trp) residues at 109, 220 and 268 has been studied using the steady state and time resolved emission of the protein and the enhanced emission of the bound drug. The association constant at 298 K (≈10(6) M) and the number of binding site (=1) were estimated using the quenched Trp emission of AP, the enhanced emission and the anisotropy of the bound drug. The values of ΔH(0) and ΔS(0) are indicative of electrostatic and H-bonding interaction. The low temperature phosphorescence of free AP and the protein- drug complex and molecular docking comprehensively prove the specific involvement of partially exposed Trp 220 in the binding process without affecting Trp 109 and Trp 268. The Förster energy transfer (ET) efficiency and the rate constant from the Trp residue to TC=0.51 and ≈10(8) s(-1) respectively. Arg 199, Glu 219, Trp 220, Lys 223, Ala 231, Arg 232 and Tyr 234 residues are involved in the binding process. The motional restriction of TC imposed by nearby residues is reflected in the observed life time and the rotational correlation time of bound TC.
盐酸四环素（TC）与碱性磷酸酶（AP）的相互作用，AP 是药物化学中的重要靶标酶，其 109、220 和 268 位含有色氨酸（Trp）残基，本研究使用蛋白的稳态和时间分辨发射以及结合药物的增强发射进行了研究。使用 AP 的猝灭 Trp 发射、增强发射和结合药物的各向异性，在 298 K（≈10(6) M)时估算了结合常数和结合位点数（=1）。ΔH(0)和ΔS(0)的值表明存在静电和氢键相互作用。游离 AP 和蛋白-药物复合物的低温磷光以及分子对接全面证明了部分暴露的 Trp 220 特异性参与了结合过程，而不会影响 Trp 109 和 Trp 268。从 Trp 残基到 TC 的福斯特能量转移（ET）效率和速率常数分别为 0.51 和≈10(8) s(-1)。Arg 199、Glu 219、Trp 220、Lys 223、Ala 231、Arg 232 和 Tyr 234 残基参与了结合过程。附近残基对 TC 的运动限制反映在观察到的结合 TC 的寿命和旋转相关时间上。
