血红素修饰对肌红蛋白氧亲合力和高铁肌红蛋白酸碱转变平衡的影响,Journal of the American Chemical Society

当前位置： X-MOL 学术 › J. Am. Chem. Soc. › 论文详情

Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)

血红素修饰对肌红蛋白氧亲合力和高铁肌红蛋白酸碱转变平衡的影响
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2010-05-05 , DOI: 10.1021/ja909891q
Tomokazu Shibata ₁ , Satoshi Nagao ₁ , Masashi Fukaya ₁ , Hulin Tai ₁ , Shigenori Nagatomo ₁ , Kenji Morihashi ₁ , Takashi Matsuo ₁ , Shun Hirota ₁ , Akihiro Suzuki ₁ , Kiyohiro Imai ₁ , Yasuhiko Yamamoto ₁

Affiliation

肌红蛋白 (Mb) 的功能调节被认为是通过附近氨基酸残基提供的血红素环境以及对内在血红素 Fe 反应性的微妙调整来实现的。我们已经进行了强吸电子全氟甲基 (CF(3)) 基团的取代作为 Mb 的血红素侧链，以获得血红素电子结构的大改变，以阐明 O(2) Mb 的亲和力和血红素外围侧链的电子特性。我们利用高铁肌红蛋白中“酸-碱转变”的平衡常数 (pK(a)) 来定量评估 CF(3) 取代对血红素 Fe 原子 (rho(Fe)) 电子密度的影响的蛋白质。在引入一个 CF(3) 基团后，发现蛋白质的 pK(a) 值降低了大约 1 个 pH 单位，并且 pK(a) 值随着 rho(Fe) 值的降低而降低，这证实了一些模型化合物的密度泛函理论计算。发现 Mb 的 O(2) 亲和力与 pK(a) 值密切相关，P(50) 值是实现 50% 氧化所需的 O(2) 分压，增加减少 1 pK(a) 单位，系数为 2.7。对蛋白质的动力学研究表明，引入吸电子 CF(3) 组后 O(2) 亲和力的降低是由于 O(2) 解离率的增加。由于引入 CF(3) 基团取代被认为可以防止进一步的 Fe(2+)-O(2) 键极化，从而防止形成推定的 Fe(3+)-O(2)(-) 类物质蛋白质的氧形式 [Maxwell, JC; 沃尔佩，JA；巴洛，CH；Caughey，WS 生物化学。生物物理学。水库社区。1974, 58, 166-171]，O(2) 解离有望通过取代吸电子基团作为血红素侧链来增强。我们还发现，与 O(2) 与蛋白质结合的情况形成鲜明对比的是，CO 关联和解离率基本上与 rho(Fe) 值无关。因此，吸电子基团的引入增强了 CO 与蛋白质的优先结合，而不是 O(2)。

"点击查看英文标题和摘要"

Effect of Heme Modification on Oxygen Affinity of Myoglobin and Equilibrium of the Acid−Alkaline Transition in Metmyoglobin

Functional regulation of myoglobin (Mb) is thought to be achieved through the heme environment furnished by nearby amino acid residues, and subtle tuning of the intrinsic heme Fe reactivity. We have performed substitution of strongly electron-withdrawing perfluoromethyl (CF(3)) group(s) as heme side chain(s) of Mb to obtain large alterations of the heme electronic structure in order to elucidate the relationship between the O(2) affinity of Mb and the electronic properties of heme peripheral side chains. We have utilized the equilibrium constant (pK(a)) of the "acid-alkaline transition" in metmyoglobin in order to quantitatively assess the effects of the CF(3) substitutions for the electron density of heme Fe atom (rho(Fe)) of the protein. The pK(a) value of the protein was found to decrease by approximately 1 pH unit upon the introduction of one CF(3) group, and the decrease in the pK(a) value with decreasing the rho(Fe) value was confirmed by density functional theory calculations on some model compounds. The O(2) affinity of Mb was found to correlate well with the pK(a) value in such a manner that the P(50) value, which is the partial pressure of O(2) required to achieve 50% oxygenation, increases by a factor of 2.7 with a decrease of 1 pK(a) unit. Kinetic studies on the proteins revealed that the decrease in O(2) affinity upon the introduction of an electron-withdrawing CF(3) group is due to an increase in the O(2) dissociation rate. Since the introduction of a CF(3) group substitution is thought to prevent further Fe(2+)-O(2) bond polarization and hence formation of a putative Fe(3+)-O(2)(-)-like species of the oxy form of the protein [Maxwell, J. C.; Volpe, J. A.; Barlow, C. H.; Caughey, W. S. Biochem. Biophys. Res. Commun. 1974, 58, 166-171], the O(2) dissociation is expected to be enhanced by the substitution of electron-withdrawing groups as heme side chains. We also found that, in sharp contrast to the case of the O(2) binding to the protein, the CO association and dissociation rates are essentially independent of the rho(Fe) value. As a result, the introduction of electron-withdrawing group(s) enhances the preferential binding of CO to the protein over that of O(2). These findings not only resolve the long-standing issue of the mechanism underlying the subtle tuning of the intrinsic heme Fe reactivity, but also provide new insights into the structure-function relationship of the protein.

更新日期：2010-05-05

点击分享查看原文

点击收藏

阅读更多本刊新发论文本刊介绍/投稿指南