Circular dichroic spectroscopy of membrane haemoproteins. The molecular determinants of the dichroic properties of the b cytochromes in various ubiquinol:cytochrome c reductases.
Circular dichroic spectroscopy of membrane haemoproteins. The molecular determinants of the dichroic properties of the b cytochromes in various ubiquinol:cytochrome c reductases.
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膜血蛋白的圆二向色光谱。
DOI：
10.1111/j.1432-1033.1989.tb14796.x
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Lenaz,G
中科院分区：
文献类型：
--
作者：
DegliEsposti,M;Palmer,G;Lenaz,G
已表征了线粒体和细菌泛醇：细胞色素还原酶（bc 1复合物）的二血红素细胞色素b的圆二色性（CD）。酵母纯化的cytbare的二色性与天然cytbwithin的cytalbc 1复合物的二色性非常相似。在所有研究物种中存在的天然细胞色素b的Soret区域的CD光谱显示出强烈的双信号Cotton效应，其零交叉波长接近最大吸光度。在部分或完全耗尽低电位血红素（b1）的制剂中，CD光谱显示出类似于相应吸收光谱的单一正Cotton效应。这在来自球形红细菌R26的纯化的细胞色素b-562中特别明显，其仅含有高电位血红蛋白（bh）。这些光谱特征与重组的cytochromeb 1haem已被用来解决的CD贡献的每个haem的CD光谱的cytochromeb.The机制可能是负责的光学活性已被检查。看来，CD光谱的cytochromebderive从两个血红素的相互作用（引起激子耦合）和每个血红素与附近的芳香族残基的相互作用，而不是对组氨酸的协调铁。血红素和芳香残基之间的偶极耦合似乎是更重要的比激子耦合在CD光谱的氧化bcytochromes和相关性之间的CD功能和建议的cytochromeb的结构。
The circular dichroism (CD) of dihaem cytochromebfrom mitochondrial and bacterial ubiquinol:cytochrome‐creductase (bc1 complex) has been characterized. The dichroic properties of the yeast purified cytbare very similar to those of the native cytbwithin the mitochondrialbc1 complex. The CD spectra in the Soret region of the native cytochromebpresent in all species studied show an intense bisignate Cotton effect having a zero‐crossing wavelength close to the absorbance maximum.In preparations partially or completely depleted of the low‐potentialbhaem (b1) the CD spectra exhibit a single positive Cotton effect resembling the corresponding absorption spectrum. This is particularly evident in the purified cytochromeb‐562 fromRhodobacter sphaeroidesR26, which contains only the high‐potentialbhaem (bh). These spectral features together with the reconstitution of the cytochromeb1haem have been used to resolve the CD contribution of each haem to the CD spectra of cytochromeb.The mechanisms which might be responsible for the optical activity have been examined. It appears that the CD spectra of cytochromebderive from both the mutual interaction of its two haems (giving rise to exciton coupling) and to the interaction of each haem with nearby aromatic residues, other than the pairs of histidines which coordinate the iron. The dipole coupling between haem and aromatic residues appears to be more important than exciton coupling in the CD spectra of oxidizedbcytochromes and correlations have been made between the CD features and the proposed structure of cytochromeb.