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首页> 外文期刊>Journal of Molecular Biology >Direct determination of protonation states of histidine residues in a 2 A neutron structure of deoxy-human normal adult hemoglobin and implications for the Bohr effect.
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Direct determination of protonation states of histidine residues in a 2 A neutron structure of deoxy-human normal adult hemoglobin and implications for the Bohr effect.

机译：直接测定脱氧人正常成年人血红蛋白的2 A中子结构中组氨酸残基的质子化状态及其对玻尔效应的影响。

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摘要

We have investigated the protonation states of histidine residues (potential Bohr groups) in the deoxy form (T state) of human hemoglobin by direct determination of hydrogen (deuterium) positions with the neutron protein crystallography technique. The reversible binding of protons is key to the allosteric regulation of human hemoglobin. The protonation states of 35 of the 38 His residues were directly determined from neutron scattering omit maps, with 3 of the remaining residues being disordered. Protonation states of 5 equivalent His residues--alpha His20, alpha His50, alpha His89, beta His143, and beta His146--differ between the symmetry-related globin subunits. The distal His residues, alpha His58 and beta His63, are protonated in the alpha 1 beta 1 heterodimer and are neutral in alpha 2 beta 2. Buried residue alpha His103 is found to be protonated in both subunits. These distal and buried residues have the potential to act as Bohr groups. The observed protonation states of His residues are compared to changes in their pK(a) values during the transition from the T to the R state and the results provide some new insights into our understanding of the molecular mechanism of the Bohr effect.
机译：我们已经通过中子蛋白质晶体学技术直接测定氢（氘）位置，研究了人类血红蛋白脱氧形式（T状态）中组氨酸残基（潜在的玻尔基）的质子化状态。质子的可逆结合是人类血红蛋白变构调节的关键。直接从中子散射省略图确定38个His残基中的35个的质子化状态，其余3个残基无序。 5个等效的His残基的质子化状态-αHis20，αHis50，αHis89，βHis143和βHis146-在与对称相关的球蛋白亚基之间存在差异。远端的His残基，即His His58和beta His63，在alpha 1 beta 1异二聚体中被质子化，而在alpha 2 beta 2中呈中性。这些远端和掩埋的残基有可能充当玻尔基团。将观察到的His残基的质子化状态与从T态到R态过渡期间其pK（a）值的变化进行比较，结果为我们对玻尔效应的分子机理的理解提供了一些新见识。

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