Shimizu T, Nozawa T, Hatano M, Satake H, Imai Y, Hashimoto C, Sato R
Biochim Biophys Acta. 1979 Jul 25;579(1):122-33. doi: 10.1016/0005-2795(79)90092-8.
Circular dichroism (CD) spectra were measured for cytochromes P-450 (P-450) purified from phenobarbital- and 3-methylcholanthrene-induced rabbit liver microsomes. No striking difference in alpha-helix content was seen between phenobarbital-induced P-450 (PB P-450) (50%), phenobarbital-induced P-448 (PB P-448) (40%) and 3-methylcholanthrene-induced P-448 (MC P-448) (45--50%) in terms of ultraviolet CD spectra. Strong negative CD spectra associated with 3-methylcholanthrene transitions for MC P-448 in the near-ultraviolet region (250--310 nm) and weaker negative CD spectra associated with Soret transitions for PBP-448 ([theta] = 50 000) and MCP-448 ([theta] = 160 000), indicated that structures of these preparations are strikingly different from each other. Reduction of P-450 and P-448 led to a remarkable decrease of the Soret CD trough, suggesting that reduction was accompanied by a striking conformational change in the vicinity of the heme. Since CO complexes of reduced P-450 and P-448 showed a CD trough and an S-shaped CD, respectively, associated with the absorption peak at 450 nm, the heme vicinities are remarkably different from each other. The CD spectra in the visible region are also discussed. It was noticed that P-420, the denatured form of P-450, exhibited no CD spectra in the Soret and visible regions.
对从苯巴比妥和3 - 甲基胆蒽诱导的兔肝微粒体中纯化得到的细胞色素P - 450（P - 450）进行了圆二色性（CD）光谱测定。就紫外CD光谱而言，苯巴比妥诱导的P - 450（PB P - 450）（50%）、苯巴比妥诱导的P - 448（PB P - 448）（40%）和3 - 甲基胆蒽诱导的P - 448（MC P - 448）（45 - 50%）之间在α - 螺旋含量上未见显著差异。在近紫外区域（250 - 310 nm），与MC P - 448的3 - 甲基胆蒽跃迁相关的强负CD光谱，以及与PBP - 448（[θ] = 50 000）和MCP - 448（[θ] = 160 000）的Soret跃迁相关的较弱负CD光谱，表明这些制剂的结构彼此显著不同。P - 450和P - 448的还原导致Soret CD谷显著降低，表明还原伴随着血红素附近显著的构象变化。由于还原型P - 450和P - 448的CO复合物分别在450 nm吸收峰处显示出一个CD谷和一个S形CD，血红素附近彼此显著不同。还讨论了可见区域的CD光谱。注意到P - 450的变性形式P - 420在Soret和可见区域均未表现出CD光谱。
