Control of distal lysine coordination in a monomeric hemoglobin: A role for heme peripheral interactions
Control of distal lysine coordination in a monomeric hemoglobin: A role for heme peripheral interactions
复制标题
单体血红蛋白远端赖氨酸协调的控制：血红素外周相互作用的作用
DOI：
10.1016/j.jinorgbio.2021.111437
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发表时间：
2021
影响因子：
3.9
通讯作者：
Lecomte, Juliette T.J.
中科院分区：
文献类型：
--
作者：
Martinez Grundman, Jaime E.;Julió Plana, Laia;Schlessman, Jamie L.;Capece, Luciana;Estrin, Darío A.;Lecomte, Juliette T.J.
THB 1是在绿色莱茵衣藻细胞质中发现的单体截短血红蛋白（TrHb）。血红蛋白中的典型血红素配位方案是近端组氨酸配体和开放的远端位点。在THB 1中，后一个位点被Lys 53占据，这可能促进Fe（II）/Fe（III）氧化还原循环，但阻碍分子氧结合，这是蛋白质的NO双加氧酶活性所固有的两个特征。TrHb调查表明，赖氨酸在与Lys 53对齐的位置是一个不足的决定因素的协调，在这项研究中，我们试图确定因素控制赖氨酸的血红素铁亲和力。我们解决了THB 1的“Lys-off”X射线结构，以Fe（III）蛋白的氰化物加合物为代表，并假设已知的“Lys-on”结构和Lys-off结构之间不同的相互作用参与控制Lys 53对血红素铁的亲和力。我们采用了实验方法（定点诱变，血红素修饰，pH滴定在Fe（III）和Fe（II）状态）和计算方法（MD模拟在Fe（II）状态），以评估血红素丙酸-蛋白质相互作用的作用，远端螺旋帽，和远端口袋的组成。所有的THB 1修饰导致赖氨酸亲和力减弱，并影响Lys 53质子结合和血红素氧化还原电位之间的耦合。这些结果支持了特定血红素外周相互作用对铁配位的pH稳定性和蛋白质进行氧化还原反应的能力的重要性。
THB1 is a monomeric truncated hemoglobin (TrHb) found in the cytoplasm of the green algaChlamydomonas reinhardtii. The canonical heme coordination scheme in hemoglobins is a proximal histidine ligand and an open distal site. In THB1, the latter site is occupied by Lys53, which is likely to facilitate Fe(II)/Fe(III) redox cycling but hinders dioxygen binding, two features inherent to the NO dioxygenase activity of the protein. TrHb surveys show that a lysine at a position aligning with Lys53 is an insufficient determinant of coordination, and in this study, we sought to identify factors controlling lysine affinity for the heme iron. We solved the “Lys-off” X-ray structure of THB1, represented by the cyanide adduct of the Fe(III) protein, and hypothesized that interactions that differ between the known “Lys-on” structure and the Lys-off structure participate in the control of Lys53 affinity for the heme iron. We applied an experimental approach (site-directed mutagenesis, heme modification, pH titrations in the Fe(III) and Fe(II) states) and a computational approach (MD simulations in the Fe(II) state) to assess the role of heme propionate–protein interactions, distal helix capping, and the composition of the distal pocket. All THB1 modifications resulted in a weakening of lysine affinity and affected the coupling between Lys53 proton binding and heme redox potential. The results supported the importance of specific heme peripheral interactions for the pH stability of iron coordination and the ability of the protein to undergo redox reactions.