INFLUENCE OF CHARGE AND POLARITY ON THE REDOX POTENTIALS OF HIGH-POTENTIAL IRON-SULFUR PROTEINS - EVIDENCE FOR THE EXISTENCE OF 2 GROUPS
INFLUENCE OF CHARGE AND POLARITY ON THE REDOX POTENTIALS OF HIGH-POTENTIAL IRON-SULFUR PROTEINS - EVIDENCE FOR THE EXISTENCE OF 2 GROUPS
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DOI：
10.1021/bi00045a008
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发表时间：
1995-11-14
期刊：
影响因子：
2.9
通讯作者：
MEYER, TE
中科院分区：
文献类型：
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作者：
HEERING, HA;BULSINK, YBM;MEYER, TE
我们用直接电化学方法研究了液泡外红螺旋菌（iso1和iso2）、vinosum染色菌、geldocyclus gelatinosus、tenusrhodocyclus（2761）、globiformrhodopila和salinarum Rhodospirillum （iso2）的HiPIPs。使用表面带负电荷的玻碳电极，可以与带正电荷的hipip进行直接的、非促进的电化学反应。对于带负电荷的hipip，需要带正电荷的柔性桥接启动子聚l -赖氨酸。morolin、天冬氨酸、色氨酸或4,4′-二吡啶可提高反应的稳定性。这些“稳定剂”可以防止变性蛋白质堵塞电极。盐海藓iso-2的氧化还原电位为500 mV，是目前报道的最高hiip电位。序列中组氨酸的存在本身并不能预测ph依赖性氧化还原电位。只有C. I vinosum和R. gelatinosus HiPIPs表现出微弱但显著的pH依赖性，低pH和高pH形式之间的差异为35 mV，最大斜率为-20 mV/单位。在不同的hipip中，中点电位对温度和离子强度的依赖性是不同的。势对根I的依赖不能用Debye-Huckel理论完全解释，因为线性超过了极限浓度，只观察到很小的负斜率（0到-28 mV/根M）。结合序列、光谱、总电荷和氧化还原热力学，表明存在两类HiPIPs。一类是类Chromatium-like hipip，氧化还原电位在300 ~ 350 mV之间，仅通过团簇的溶剂化调节。第二组是由类似异硫螺旋体的hipip形成的，其电位在50到500 mV之间，由肽的总电荷（25 mV/单位）和簇的溶剂化调节。
We have investigated the HiPIPs from Ectothiorhodospira vacuolata (iso-l and iso-2), Chromatium vinosum, Rhodocyclus gelatinosus, Rhodocyclus tenuis (strain 2761), Rhodopila globiformis, and Rhodospirillum salinarum (iso-2) by direct electrochemistry. Using a glassy carbon electrode with a negatively charged surface, direct, unpromoted electrochemistry is possible with the positively charged HiPIPs. With the negatively charged HiPIPs, the positively charged and flexible bridging promoter poly (L-lysine) is required. The stability of the response can be improved by morpholin, aspartate, tryptophan, or 4,4'-dipyridyl. These ''stabilizers'' prevent the blocking of the electrode by denatured protein. The redox potential of 500 mV found for R. salinarum iso-2 is the highest HiPIP potential reported. The presence of histidines in the sequence does not per se predict a pH-dependent redox potential. Only C. I vinosum and R. gelatinosus HiPIPs show a weak but significant pH dependence with a difference of 35 mV between the low- and the high-pH form and maximum slopes of -20 mV/unit. The dependence of the midpoint potential on temperature and on ionic strength varies over the different HiPIPs. The dependence of the potentials on root I cannot be fully explained by the Debye-Huckel theory because the linearity exceeds the limiting concentration and only small negative slopes are observed (0 to -28 mV/root M). Combination of the sequences, the optical spectra, the overall charges, and the redox thermodynamics suggests the existence of two groups of HiPIPs. One group consists of Chromatium-like HiPIPs with redox potentials between 300 and 350 mV, modulated only by the solvation of the cluster. The second group is formed by Ectothiorhodospira-like HiPIPs with potentials between 50 and 500 mV, modulated by the overall charge of the Peptide (25 mV/unit) and by the solvation of the cluster.