Protein conformation changes of HemAT-Bs upon ligand binding probed by ultraviolet resonance Raman spectroscopy
Protein conformation changes of HemAT-Bs upon ligand binding probed by ultraviolet resonance Raman spectroscopy
复制标题
DOI：
10.1074/jbc.m709209200
复制
发表时间：
2008-03-14
影响因子：
4.8
通讯作者：
Kitagawa, Teizo
中科院分区：
文献类型：
--
作者：
El-Mashtoly, Samir F.;Gu, Yuzong;Kitagawa, Teizo
来自枯草芽孢杆菌 (HemAT-Bs) 的 HemAT 是一种基于血红素的 O-2 传感器蛋白，充当负责通气的信号传感器。 HemAT-Bs 将其生理效应子 (O-2) 与其他气体分子（CO 和 NO）区分开来，尽管它们都与血红素结合。为了监测不同配体结合后蛋白质部分的构象变化，我们研究了全长HemAT-Bs和几种突变体（Y70F、H86A、T95A和Y133F）的无配体和O-2-、CO-和NO结合形式的紫外共振拉曼（UVRR）光谱，发现血红素远端的Tyr（70）和Tyr（133）和血红素近侧 G 螺旋的 Trp(132) 在配体结合时经历环境变化。此外，UVRR 结果证实了我们之前的模型，该模型表明 Thr(95) 与血红素结合的 O-2 形成氢键，但 Tyr(70) 则没有。从这项研究中推断，Thr(95) 和血红素结合的 O-2 之间以及 His(86) 和血红素 6-丙酸盐之间的氢键在 O-2 结合时将血红素结构变化传达给蛋白质部分，但在 CO 和 NO 结合时则不然。因此，目前的 UVRR 结果表明，O-2 与血红素的结合导致 G 螺旋的移位，这对于从传感器结构域到信号传导结构域的构象变化的转导非常重要。
HemAT from Bacillus subtilis (HemAT-Bs) is a heme-based O-2 sensor protein that acts as a signal transducer responsible for aerotaxis. HemAT-Bs discriminates its physiological effector (O-2) from other gas molecules (CO and NO), although all of them bind to a heme. To monitor the conformational changes in the protein moiety upon binding of different ligands, we have investigated ultraviolet resonance Raman (UVRR) spectra of the ligand-free and O-2-, CO-, and NO-bound forms of full-length HemAT-Bs and several mutants (Y70F, H86A, T95A, and Y133F) and found that Tyr(70) in the heme distal side and Tyr(133) and Trp(132) from the G-helix in the heme proximal side undergo environmental changes upon ligand binding. In addition, the UVRR results confirmed our previous model, which suggested that Thr(95) forms a hydrogen bond with heme-bound O-2, but Tyr(70) does not. It is deduced from this study that hydrogen bonds between Thr(95) and heme-bound O-2 and between His(86) and heme 6-propionate communicate the heme structural changes to the protein moiety upon O-2 binding but not upon CO and NO binding. Accordingly, the present UVRR results suggest that O-2 binding to heme causes displacement of the G-helix, which would be important for transduction of the conformational changes from the sensor domain to the signaling domain.