Evidence for displacements of the C-helix by CO Ligation and DNA binding to CooA revealed by UV resonance Raman spectroscopy
Evidence for displacements of the C-helix by CO Ligation and DNA binding to CooA revealed by UV resonance Raman spectroscopy
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DOI：
10.1074/jbc.m513261200
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发表时间：
2006-04-21
影响因子：
4.8
通讯作者：
Kitagawa, T
中科院分区：
文献类型：
--
作者：
Kubo, M;Inagaki, S;Kitagawa, T
本文报道了红红螺旋菌（Rhodospirillum rubrum）中CooA的紫外和可见共振拉曼光谱，红红螺旋菌是一种在CO气氛中生长的转录调节剂。CO在其传感区域与血红素结合，导致其DNA结合区域重排，允许DNA与特定序列结合。传感器和dna结合域由一个铰链区域连接，该铰链区域遵循一个长c螺旋。c -螺旋中Trp-110产生的紫外共振拉曼带显示了CO结合时Trp-110周围的局部运动。Trp-110的吲哚侧链暴露于无co -亚铁态的溶剂中，被埋没在co -键态中，其取向发生轻微变化，但在吲哚氮上与水分子保持氢键。这是第一个实验数据支持先前提出的涉及c -螺旋位移和血红素滑动的模型。CooA-DNA复合物的紫外共振拉曼光谱表明，DNA与CooA结合后，在过渡到完全活性构象的过程中，c -螺旋进一步向同一方向移位。Fe-CO和C-O拉伸带在DNA结合时出现频率偏移，而Fe-His拉伸带则没有。此外，CO-geminate在dna结合状态下重组效率更高。这些结果表明，dna结合形式的c -螺旋位移导致CO结合口袋变窄并变得更负。
The UV and visible resonance Raman spectra are reported for CooA from Rhodospirillum rubrum, which is a transcriptional regulator activated by growth in a CO atmosphere. CO binding to heme in its sensor domain causes rearrangement of its DNA-binding domain, allowing binding of DNA with a specific sequence. The sensor and DNA-binding domains are linked by a hinge region that follows a long C-helix. UV resonance Raman bands arising from Trp-110 in the C-helix revealed local movement around Trp-110 upon CO binding. The indole side chain of Trp-110, which is exposed to solvent in the CO-free ferrous state, becomes buried in the CO-bound state with a slight change in its orientation but maintains a hydrogen bond with a water molecule at the indole nitrogen. This is the first experimental data supporting a previously proposed model involving displacement of the C-helix and heme sliding. The UV resonance Raman spectra for the CooA-DNA complex indicated that binding of DNA to CooA induces a further displacement of the C-helix in the same direction during transition to the complete active conformation. The Fe-CO and C-O stretching bands showed frequency shifts upon DNA binding, but the Fe-His stretching band did not. Moreover, CO-geminate recombination was more efficient in the DNA-bound state. These results suggest that the C-helix displacement in the DNA-bound form causes the CO binding pocket to narrow and become more negative.