Jagath J R, Rodnina M V, Wintermeyer W
Institut für Molekularbiologie, Universität Witten/Herdecke, Witten, 58448, Germany.
J Mol Biol. 2000 Jan 28;295(4):745-53. doi: 10.1006/jmbi.1999.3427.
In cotranslational preprotein targeting in Escherichia coli, the signal recognition particle (SRP) binds to the signal peptide emerging from the ribosome and, subsequently, interacts with the signal recognition particle receptor, FtsY, at the plasma membrane. Both FtsY and the protein moiety of the signal recognition particle, Ffh, are GTPases, and GTP is required for the formation of the SRP-FtsY complex. We have studied the binding of GTP/GDP to FtsY as well as the SRP-FtsY complex formation by monitoring the fluorescence of tryptophan 343 in the I box of mutant FtsY. Thermodynamic and kinetic parameters of the FtsY complexes with GDP, GTP, and signal recognition particle are reported. Upon SRP-FtsY complex formation in the presence of GTP, the fluorescence of tryptophan 343 increased by 50 % and was blue-shifted by 10 nm. We conclude that GTP-dependent SRP-FtsY complex formation leads to an extensive conformational change in the I box insertion in the effector region of FtsY.
在大肠杆菌的共翻译前体蛋白靶向过程中，信号识别颗粒（SRP）与从核糖体中露出的信号肽结合，随后与质膜上的信号识别颗粒受体FtsY相互作用。FtsY和信号识别颗粒的蛋白质部分Ffh都是GTP酶，并且形成SRP - FtsY复合物需要GTP。我们通过监测突变型FtsY的I框中色氨酸343的荧光，研究了GTP / GDP与FtsY的结合以及SRP - FtsY复合物的形成。报告了FtsY与GDP、GTP和信号识别颗粒形成复合物的热力学和动力学参数。在GTP存在下形成SRP - FtsY复合物时，色氨酸343的荧光增加了50%，并且蓝移了10 nm。我们得出结论，GTP依赖的SRP - FtsY复合物形成导致FtsY效应区域中I框插入发生广泛的构象变化。
