MULTINUCLEAR & MULTIDIMENSIONAL NMR SPECT STUDIES OF HUMAN PLACENTAL FERREDOXIN

人类铁氧还蛋白属于脊椎动物铁氧还蛋白家族， 其中包括牛肾上腺素。它是一种小(13.8 kDa)酸性物质 具有[2Fe-2S]簇的蛋白质。它的功能就像一个电子穿梭机 在胆固醇侧链裂解反应中，这是第一个 类固醇激素生物合成步骤。这里研究的蛋白质是 在大肠杆菌中生产，并用13C和15N双重标记。这个 抗磁性15N，13C？，13C？，13C？，1H？和大约1HN的共振 氧化型人铁还蛋白的124个氨基酸残基中的70%和 80%的还原蛋白质主要被分配到 三维三重共振结果的基础 实验。氧化蛋白的二级结构特征有 由化学位移指数和化学位移指数的组合确定 连续的NOE数据，以及还原蛋白质的数据 由化学位移指数分析得出。结构形式的比较 有关氧化和还原蛋白质的信息显示， 结构变化伴随着[2Fe-2S]团簇的减少。 主要的结构变化局限于两个区域：残基29？31 和残基109？124，它们构成了C端区域的一部分 蛋白。它们可能的功能意义 讨论了氧化态相关的结构变化。

Human ferredoxin belongs to the vertebrate ferredoxin family, which includes bovine adrenodoxin. It is a small (13.8 kDa) acidic protein with a [2Fe-2S] cluster. It functions as an electron shuttle in the cholesterol side-chain cleavage reaction, which is the first step of steroid hormone biosynthesis. The protein studied here was produced in Escherichia coli and doubly labeled with 13C and 15N. The diamagnetic 15N, 13C?, 13C?, 13C?, 1H? and 1HN resonances from about 70% of the 124 amino acid residues for oxidized human ferredoxin and 80% of those for the reduced protein have been assigned primarily on the basis of results from three-dimensional, triple-resonance experiments. Secondary structure features for oxidized protein have been identified from a combination of the chemical shift index and sequential NOE data, and those for the reduced protein have been deduced from chemical shift index analysis. Comparison of structural information on the oxidized and reduced proteins reveals that a structural change accompanies the reduction of the [2Fe-2S] cluster. Major structural changes are localized at two regions: residues 29?31 and residues 109?124, which form part of the C-terminal region of the protein. The possible functional significance of these oxidation-state-dependent structural changes is discussed.