Salmeen I, Rimai L, Babcock G
Biochemistry. 1978 Mar 7;17(5):800-6. doi: 10.1021/bi00598a008.
We report 441.6 nm excitation resonance Raman spectra of oxidized and reduced monomeric heme a-imidazole, cytochrome oxidase-exogenous ligand complexes in various redox states, and alkaline denatured oxidase. These data show that, in reduced oxidase, the cytochrome a3 Raman spectrum has bands at 215, 364, 1230, and 1670 cm-1 not observed in the cytochrome a spectrum. The appearance of these bands in the reduced cytochrome a3 spectrum is due to interactions between the heme a of cytochrome a3 and its protein environment and not to intrinsic properties of heme a. These interactions are pH sensitive and strongly influence the vibrational spectra of both heme a groups. We assign the 1670-cm-1 band to the heme a formyl substituent and propose that the intensity of the 1670 cm-1 is high for reduced cytochrome a3 because the C==O lies in the porphyrin plane and is very weak for oxidized and reduced cytochrome a, oxidized cytochrome a3, and oxidized and reduced heme a-imidazole because the C==O lies out of the plane. We suggest that movement of the C==O in and out of the plane explains the ligand induced spectral shift in the optical absorption spectrum of reduced cytochrome a3. Finally, we confirm the observation of Adar & Yonetani (private communication) that, under laser illumination, resting oxidase is photoreactive.
我们报告了氧化态和还原态的单体血红素a-咪唑、处于各种氧化还原状态的细胞色素氧化酶-外源性配体复合物以及碱性变性氧化酶的441.6 nm激发共振拉曼光谱。这些数据表明，在还原态氧化酶中，细胞色素a3的拉曼光谱在215、364、1230和1670 cm-1处有细胞色素a光谱中未观察到的谱带。这些谱带在还原态细胞色素a3光谱中的出现是由于细胞色素a3的血红素a与其蛋白质环境之间的相互作用，而非血红素a的固有特性。这些相互作用对pH敏感，并强烈影响两个血红素a基团的振动光谱。我们将1670 cm-1的谱带归属于血红素a的甲酰基取代基，并提出对于还原态细胞色素a3，1670 cm-1处谱带的强度较高是因为C==O位于卟啉平面内，而对于氧化态和还原态的细胞色素a、氧化态细胞色素a3以及氧化态和还原态的血红素a-咪唑，该谱带强度较弱是因为C==O位于平面外。我们认为C==O进出平面的移动解释了还原态细胞色素a3的光吸收光谱中配体诱导的光谱位移。最后，我们证实了阿达和米谷达尼（私人通信）的观察结果，即在激光照射下，静止的氧化酶具有光反应性。
