Circular dichroism of cytochrome cc' and cytochrome c'.
Circular dichroism of cytochrome cc' and cytochrome c'.
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细胞色素cc和细胞色素c的圆二色性。
DOI：
10.1093/oxfordjournals.jbchem.a129056
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发表时间：
1969
影响因子：
2.7
通讯作者：
T. Horio
中科院分区：
文献类型：
--
作者：
Y. Imai;K. Imai;K. Ikeda;K. Hamaguchi;T. Horio
在205 - 500 μ m范围内，测定了红杜鹃和沼泽红杜鹃细胞色素在不同条件下的圆二色性（CD）。在pH7时，氧化型细胞色素c ′在Soret区406 m μ处有一个CD正极值，在δ区325 - 360 m μ处有一个宽的CD负带，在芳香区260 - 285 m μ处有一个CD正极值。远紫外区的CD谱在222和207 m μ处出现负极值，这是α-螺旋的特征。螺旋含量计算为约63%。在Soret、δ和芳香区的CD光谱可以通过伴随吸收光谱变化的环境而改变。在芳香区的CD光谱，这是平行于那些在Soret区域的变化，表明在芳香区的CD频带反映的血红素基团的环境。在细胞色素c中加入25%的2-丙醇，使Soret、δ和芳香区的吸收光谱和CD光谱从中性转变为碱性，但远紫外区的CD光谱基本上没有变化。在pH为12.3的2 m KCl存在下，吸收光谱为中间型，远紫外区的CD光谱也为相同的中间型。在不存在KCl的情况下，222 m μ处的负带在pH 12.3时大大减弱。在室温和pH 7下用6M尿素处理20小时，会引起螺旋结构的相当大的破坏，但在Soret、δ和芳香区域中仅产生朝向碱性类型的微小变化。当在加入尿素后立即检查样品时，在整个波长范围内仅发现轻微变化。在细胞色素上也得到了类似的结果。这些发现表明，从中性到碱性的吸收光谱的变化不一定伴随着蛋白质部分的总螺旋构象的变化，这可能保护血红素的特殊环境。
The circular dichroism (CD)**of cytochromecc'' fromRhodospirillum rubrumand cytochromec'' fromRhodopseudomonas palustriswas measured in the 205–500mμ region under various conditions where the cytochromes show different types of absorption spectra. At pH 7 the oxidized form of cytochromecc' exhibits a positive CD extremum at 406 mμ in the Soret region, a broad negative CD band from 325 to 360mμ in the δ region, and positive extrema between 260 and 285mμ in the aromatic region. The CD spectrum in the far-ultraviolet region exhibits negative extrema at 222 and 207mμ, which are characteristic of the a-helix. The helical content is calculated to be about 63%. The CD spectra in the Soret, δ, and aromatic region can be changed by the environment concomitant with changes in the absorption spectra. Changes in the CD spectrum in the aromatic region, which are parallel to those in the Soret region, indicate that the CD bands in the aromatic region reflect the environment of the heme groups. Addition of 25% 2-propanol to cytochromecc, which results in the conversion of the absorption spectrum and the CD spectrum in the Soret, δ, and aromatic regions from the neutral to the alkaline type, causes essentially no change in the CD spectrum in the far-ultraviolet region. In the presence of 2 m KC1 at pH 12.3, where the absorption spectrum is of the intermediate type, the CD spectrum in the far-ultraviolet region is also the same intermediate type. In the absence of KC1 the negative band at 222 mμ is greatly diminished at pH 12.3. Treatment with 6 m urea for 20 hr at room temperature at pH 7 causes considerable destruction of the helical structure but produces only a small change toward the alkaline type in the Soret, δ, and aromatic regions. Only slight changes are found in the whole wavelength range when the sample is examined immediately after the addition of urea. Similar results are obtained on cytochromec'.These findings suggest that the change in the absorption spectrum from the neutral to the alkaline type is not necessarily accompanied by a change in the gross helical conformation of the protein moiety which might protect the special environment of the heme.