Assignments of 15N and 1H NMR resonances and a neutral pH ionization in Rhodospirillum rubrum cytochrome c2.
Assignments of 15N and 1H NMR resonances and a neutral pH ionization in Rhodospirillum rubrum cytochrome c2.
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红色红螺菌细胞色素 c2 中 15N 和 1H NMR 共振和中性 pH 电离的归属。
DOI：
10.1021/bi00464a004
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发表时间：
1990
期刊：
影响因子：
2.9
通讯作者：
Smith,GM
中科院分区：
文献类型：
--
作者：
Yu,LP;Smith,GM
加州大学食品科学与技术系，Davis，加州，95616接收于1989年4月14日;修订的Mandarin pt接收于1989年11月21日摘要：发现红色红杜鹃铁细胞色素c2的配体组氨酸的质子和15 N共振分别为14.7和184 ppm，这与红杜鹃中不存在该质子的假设相矛盾。红铁细胞色素氘原子取代这个质子导致小的高场位移的氮在两个氧化态，表明肽羧基氢键是没有实质性削弱的取代。质子和15 N共振的吲哚NH组不变的色氨酸-62和众多的质子共振的血红素和extraheme配体的光谱中的ferricytochrome也被分配。在中性pH值下发生的铁细胞色素的电离被分配给单个非配体组氨酸。这一属性是支持的电离NOE差光谱的直接测量和比较结构的参数，涉及密切相关的细胞色素和化学修饰的细胞色素。核磁共振波谱在表征包括细胞色素C的电子转移蛋白质中起着重要作用。线粒体细胞色素c的溶液和晶体结构之间的细微结构差异已经通过NMR技术证明（摩尔等人，1985;威廉姆斯等人，1985 a，B），因为在红杜鹃细胞色素c2中的血红素丙酸基团和环周围具有构象变化（Yu & Smith，1988 a，B）。甚至已经研究了不同细胞色素c中的铁配位的立体化学，并且发现其是不同的（Senn & Wuthrich，1983 a，B; Senn等人，1983年b）。电离对细胞色素c的氧化还原性质的影响也已经通过使用NMR技术进行了研究（摩尔等人，1980，1984; Leitch等人，1984年）。使用NMR技术进行结构解释的主要问题是解析单个共振并将其分配给分子中的单个原子。血红素、轴向配体甲硫氨酸和组氨酸以及其他残基的归属已被报道（Keller & Wuthrich，1978 a;摩尔&威廉姆斯，1980 a-f，1984）。线粒体细胞色素（马）的质子NMR谱最近已被指定（Wand等人，1989; Feng等人，1989年）。然而，在两种氧化态的细菌细胞色素的重要基团的分配是不完整的，包括几个重要的共振附近的血红素铁，如配体组氨酸质子和C2质子在氧化态。这些共振在表征配体组氨酸的状态时特别重要（Brautigan等人，1977），以及氧化和还原的细胞色素在内部电荷，疏水性，可交换质子的交换率，氢键和局部动力学方面的结构差异。它们对解释氧化还原电位随pH的变化也很重要。
Department of Food Science and Technology, University of California, Davis, California 95616 Received April 14, 1989; Revised Manuscript Received November 21, 1989 abstract: The proton and 15N resonances of the ligand histidine of Rhodospirillum rubrum ferricytochrome c2 are found at 14.7 and 184 ppm, respectively, contradicting the proposal that this proton is absent in the R. rubrum ferricytochrome. Substitution of the deuterium atom for this proton causes small upfield shifts of the nitrogen in both oxidation states, indicating that the-peptide carboxyl hydrogen bond is not substantially weakened by the substitution. The proton and 15N resonances of the indolic NH group of the invariant tryptophan-62 and numerous proton resonances of the heme and extraheme ligands in the spectrum of the ferricytochrome are also assigned. An ionization in the ferrocytochrome occurring at neutralpH is assignedto the single nonligand histidine. This attribution is supported by the direct measurement of the ionization by NOE difference spectroscopy and by comparative structural arguments involving closely related cytochromes and chemically modified cytochromes. uclear magnetic resonance spectroscopy has played an important role in characterizing electron-transfer proteins including cytochromes c. Subtle structural differences between the solution and crystal structures of mitochondrial cytochrome c have been demonstrated by NMR techniques (Moore et al., 1985; Williams et al., 1985a, b), as have conformational changes around the heme propionic acid groups and the loop in Rhodospirillum rubrum cytochrome c2 (Yu & Smith, 1988a, b). Even the stereochemistry of the iron coordination in different cytochromes c has been investigated and found to be different (Senn & Wuthrich, 1983a, b; Senn et al., 1983b). The influence of ionizations on the redox properties of cytochromes c has also been investigated by using NMR techniques (Moore et al., 1980, 1984; Leitch et al., 1984). The primary problem in the structural interpretation using NMR techniques is that of resolving individual resonances and assigning them to individual atoms in the molecule. The assignments for theheme, axial ligand methionine and his-tidine, and other residues have been reported (Keller & Wuthrich, 1978a; Moore & Williams, 1980a-f, 1984). The proton NMR spectra of the mitochondrial cytochrome (horse) have recently been assigned (Wand et al., 1989; Feng et al., 1989). However, the assignments of important groups in both oxidation states of the bacterial cytochromes are incomplete, including several important resonances near the heme iron, such as the ligand histidine proton and the C2 proton in the oxidized state. These resonances are particularly important in characterizing the state of the ligand histidine (Brautigan et al., 1977), and the structural differencebetween the oxidized and reduced cytochromes in terms of internal charge, hydrophobicity, exchange rates of exchangeable protons, hydrogen bonding, and local dynamics. They are also important in explaining the variation of redox potentialwith pH.