Anderson Janet S, Mustafi Sourajit M, Hernández Griselda, LeMaster David M
Department of Chemistry, Union College, Schenectady, NY 12308, United States.
Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY 12201, United States.
Biophys Chem. 2014 Aug;192:41-8. doi: 10.1016/j.bpc.2014.06.004. Epub 2014 Jun 24.
In solution, the Trp 59 indole ring at the base of the active site cleft in the FKBP domain protein FKBP12 is rotated by ~90° at a population level of 20%, relative to its canonical crystallographic orientation. NMR measurements on the homologous FK1 domains of human FKBP51 and FKBP52 indicate no observable indole ring flip conformation, while the V101I variant of FKBP12 decreases the population having a perpendicular indole orientation by 10-fold. A set of three parallel 400 ns CHARMM27 molecular simulations for both wild type FKBP12 and the V101I variant examined how this ring flip might be energetically coupled to a transition of the Glu 60 sidechain which interacts with the backbone of the 50's loop located ~12 Å from the indole nitrogen. Analysis of the transition matrix for the local dynamics of the Glu 60 sidechain, the Trp 59 sidechain, and of the structurally interposed α-helix hydrogen bonding pattern yielded a statistical allosteric coupling of 10 kJ/mol with negligible concerted dynamical coupling for the transitions of the two sidechains.
在溶液中，FKBP结构域蛋白FKBP12活性位点裂隙底部的色氨酸59吲哚环相对于其标准晶体学取向，在20%的群体水平上旋转了约90°。对人FKBP51和FKBP52同源FK1结构域的核磁共振测量表明，未观察到吲哚环翻转构象，而FKBP12的V101I变体使具有垂直吲哚取向的群体减少了10倍。针对野生型FKBP12和V101I变体进行了一组三次并行的400纳秒CHARMM27分子模拟，研究了这种环翻转如何在能量上与谷氨酸60侧链的转变相耦合，该侧链与位于距吲哚氮约12 Å处的50's环主链相互作用。对谷氨酸60侧链、色氨酸59侧链以及结构上插入的α-螺旋氢键模式的局部动力学转变矩阵进行分析，得出两个侧链转变的统计变构耦合为10 kJ/mol，协同动力学耦合可忽略不计。
