Carter C W
J Biol Chem. 1977 Nov 10;252(21):7802-11.
Active sites of Chromatium high potential iron protein (HiPIP) and Pseudomonas Aerogenes ferredoxin can be brought into equivalent orientations by assuming that their Fe4S4Sgamma4 clusters have the effective symmetry of the non-axial molecular point group Cs. Previously undetected analogies between the two proteins emerge as a result of selecting a common orientation in this mammer. Polypeptide segments connecting Cys 46 to Cys 63 in HiPIP and Cys 18 to Cys 35 in ferredoxin are analogous in the sense that they are the same length, they connect equivalent cysteinyl sulfur atoms, and they have similar, twisted antiparalled beta conformations. Tyrosine residues 19 (HiPIP) and 2 (ferredoxin) are analogous in the sense that they interact closely with equivalent inorganic sulfur atoms. To a good approximation, interactions with the polypeptide backbone and with tyrosine side chains in the two proteins place their Fe4S4Sgamma4 moieties into diastereomeric environments, which would be expected to induce different physical and chemical behavior. Circular dichroism spectra of native and super reducible HiPIP (Cammack, R. (1973) Biochem. Biophys. Res. Commun. 54, 548-554) suggest that this relationship can help to explain the contrasting oxidoreduction properties of the two proteins.
通过假定嗜色菌属高电位铁蛋白（HiPIP）和产气假单胞菌铁氧化还原蛋白的Fe4S4Sγ4簇具有非轴向分子点群Cs的有效对称性，可使它们的活性位点具有等效取向。以这种方式选择共同取向的结果是，发现了这两种蛋白质之间以前未被检测到的相似性。连接HiPIP中半胱氨酸46至半胱氨酸63以及铁氧化还原蛋白中半胱氨酸18至半胱氨酸35的多肽片段具有相似性，因为它们长度相同，连接等效的半胱氨酰硫原子，并且具有相似的扭曲反平行β构象。酪氨酸残基19（HiPIP）和2（铁氧化还原蛋白）具有相似性，因为它们与等效的无机硫原子紧密相互作用。在很好的近似程度上，两种蛋白质中与多肽主链和酪氨酸侧链的相互作用将它们的Fe4S4Sγ4部分置于非对映异构环境中，预计这会诱导不同的物理和化学行为。天然和超可还原HiPIP的圆二色光谱（Cammack，R.（1973）Biochem.Biophys.Res.Commun.54，548 - 554）表明，这种关系有助于解释这两种蛋白质截然不同的氧化还原特性。
