Yoshimura Hideaki, Yoshioka Shiro, Mizutani Yasuhisa, Aono Shigetoshi
Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan.
Biochem Biophys Res Commun. 2007 Jun 15;357(4):1053-7. doi: 10.1016/j.bbrc.2007.04.041. Epub 2007 Apr 18.
HemAT-Bs is the heme-based O(2) sensor responsible for aerotaxis control in Bacillus subtilis. In this study, we measured the time-resolved resonance Raman spectra of full-length HemAT-Bs wild-type (WT) and Y133F in the deoxy form and the photoproduct after photolysis of CO-bound form. In WT, the nu(Fe-His) band for the 10 ps photoproduct was observed at higher frequency by about 2 cm(-1) compared with that of the deoxy form. This frequency difference is relaxed in hundreds of picoseconds. This time-dependent frequency shift would reflect the conformational change of the protein matrix. On the other hand, Y133F mutant did not show such a substantial nu(Fe-His) frequency shift after photolysis. Since a hydrogen bond to the proximal His induces an up-shift of the nu(Fe-His) frequency, these results indicate that Tyr133 forms a hydrogen bond to the proximal His residue upon the ligand binding. We discuss a functional role of this hydrogen bond formation for the signal transduction in HemAT-Bs.
HemAT-Bs是枯草芽孢杆菌中负责趋氧性控制的基于血红素的O₂传感器。在本研究中，我们测量了全长HemAT-Bs野生型（WT）和Y133F在脱氧形式以及CO结合形式光解后的光产物的时间分辨共振拉曼光谱。在WT中，与脱氧形式相比，10皮秒光产物的ν(Fe-His)带在更高频率处被观察到，约高2 cm⁻¹。这种频率差异在数百皮秒内松弛。这种随时间的频率偏移将反映蛋白质基质的构象变化。另一方面，Y133F突变体在光解后未显示出如此大的ν(Fe-His)频率偏移。由于与近端His的氢键会导致ν(Fe-His)频率上移，这些结果表明Tyr133在配体结合时与近端His残基形成氢键。我们讨论了这种氢键形成在HemAT-Bs信号转导中的功能作用。
