Satterlee J D, Moench S J, Erman J E
Biochim Biophys Acta. 1987 Mar 18;912(1):87-97. doi: 10.1016/0167-4838(87)90251-2.
Cytochrome-c peroxidase (ferrocytochrome-c:hydrogen-peroxide oxidoreductase, EC 1.11.1.5) forms a noncovalent 1:1 complex with horse cytochrome c in low ionic strength solution that is detectable by proton NMR spectroscopy. When the entire proton hyperfine-shifted spectrum is considered only five hyperfine resonances exhibit unambiguously detectable shifts: the heme 8-CH3 and 3-CH3 resonances, single proton resonances near 19 ppm and -4 ppm and the methionine-80 methyl group. These shifts are very similar to those observed for the covalently crosslinked complex of cytochrome-c peroxidase and horse cytochrome c, but different from those reported for cytochrome c complexes with flavodoxin and cytochrome b5. By comparison with the shifts reported for lysine-13-modified cytochrome c we conclude that the results reported here support the Poulos-Kraut proposed structure for the molecular redox complex between cytochrome-c peroxidase and cytochrome c. These results indicate that the principal site of interaction with cytochrome-c peroxidase is the exposed heme edge of horse cytochrome c, in proximity to lysine-13 and the heme pyrrole II. The noncovalent cytochrome-c peroxidase-cytochrome c complex exists in the rapid-exchange time limit even at 500 mHz proton frequency. Our data provide an improved estimate of the minimum off-rate for exchanging cytochrome c as 1133 (+/- 120) s-1 at 23 degrees C.
细胞色素 c 过氧化物酶（亚铁细胞色素 c：过氧化氢氧化还原酶，EC 1.11.1.5）在低离子强度溶液中与马细胞色素 c 形成非共价的 1:1 复合物，该复合物可用质子核磁共振光谱检测到。当考虑整个质子超精细位移光谱时，只有五个超精细共振显示出明确可检测到的位移：血红素 8-CH3 和 3-CH3 共振、19 ppm 和 -4 ppm 附近的单个质子共振以及甲硫氨酸 -80 甲基。这些位移与细胞色素 c 过氧化物酶和马细胞色素 c 的共价交联复合物所观察到的位移非常相似，但与细胞色素 c 与黄素氧还蛋白和细胞色素 b5 的复合物所报道的位移不同。通过与赖氨酸 -13 修饰的细胞色素 c 所报道的位移进行比较，我们得出结论，此处报道的结果支持 Poulos-Kraut 提出的细胞色素 c 过氧化物酶和细胞色素 c 之间分子氧化还原复合物的结构。这些结果表明，与细胞色素 c 过氧化物酶相互作用的主要位点是马细胞色素 c 暴露的血红素边缘，靠近赖氨酸 -13 和血红素吡咯 II。即使在 500 mHz 质子频率下，非共价的细胞色素 c 过氧化物酶 - 细胞色素 c 复合物也存在于快速交换时间极限内。我们的数据提供了一个改进的估计值，即 23℃ 时细胞色素 c 交换的最小解离速率为 1133（±120）s-1。
