Replacement of the heme axial lysine as a test of conformational adaptability in the truncated hemoglobin THB1
Replacement of the heme axial lysine as a test of conformational adaptability in the truncated hemoglobin THB1
复制标题
替换血红素轴向赖氨酸作为截短血红蛋白 THB1 构象适应性的测试
DOI：
10.1016/j.jinorgbio.2019.110824
复制
发表时间：
2019
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：
Nye, Dillon B.;Johnson, Eric A.;Mai, Melissa H.;Lecomte, Juliette T.J.
氨基酸替换是一种有用的策略，以评估天然血红素蛋白的功能中的轴向血红素配体的作用。THB 1是莱茵衣原体THB 1基因的蛋白质产物，是一组1截短的血红蛋白，其使用E螺旋中的赖氨酸残基（Lys53，参照肌红蛋白在位置E10）作为中性pH下的铁配体。系统发育证据表明，许多同源蛋白质在相同位置具有组氨酸、甲硫氨酸或精氨酸。在THB 1中，如果取代天然赖氨酸作为轴向配体，则预期这些氨基酸各自传递不同的反应特性。为了探索组1截短的Hb折叠支持替代连接方案和远端口袋构象的能力，通过电子吸收、EPR和NMR光谱研究了THB 1变体K53 A（作为对照）、K53 H、K53 M和K53 R的性质。我们发现，His53能够在Fe（III）和Fe（II）状态下进行血红素连接，Met53只能在Fe（II）状态下进行配位，Arg53在Fe（III）状态下稳定氢氧化物配体。这些数据表明，第1组截短的血红蛋白折叠可以容忍不同的重排血红素环境，并具有强烈的倾向，使用两个蛋白质侧链作为铁配体，尽管伴随的结构扰动。获得各种氧化还原对和不同的pH值的反应，使这种蛋白质的血红素连接的充满活力和动态的研究一个很好的测试案例。
Amino acid replacement is a useful strategy to assess the roles of axial heme ligands in the function of native heme proteins. THB1, the protein product of theChlamydomonas reinhardtiiTHB1gene, is a group 1 truncated hemoglobin that uses a lysine residue in the E helix (Lys53, at position E10 by reference to myoglobin) as an iron ligand at neutral pH. Phylogenetic evidence shows that many homologous proteins have a histidine, methionine or arginine at the same position. In THB1, these amino acids would each be expected to convey distinct reactive properties if replacing the native lysine as an axial ligand. To explore the ability of the group 1 truncated Hb fold to support alternative ligation schemes and distal pocket conformations, the properties of the THB1 variants K53A as a control, K53H, K53M, and K53R were investigated by electronic absorption, EPR, and NMR spectroscopies. We found that His53 is capable of heme ligation in both the Fe(III) and Fe(II) states, that Met53 can coordinate only in the Fe(II) state, and that Arg53 stabilizes a hydroxide ligand in the Fe(III) state. The data illustrate that the group 1 truncated Hb fold can tolerate diverse rearrangement of the heme environment and has a strong tendency to use two protein side chains as iron ligands despite accompanying structural perturbations. Access to various redox pairs and different responses to pH make this protein an excellent test case for energetic and dynamic studies of heme ligation.