Unusual ligand discrimination by a myoglobin reconstituted with a hydrophobic domain-linked heme
Unusual ligand discrimination by a myoglobin reconstituted with a hydrophobic domain-linked heme
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DOI：
10.1021/ja044984u
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发表时间：
2005-01-12
影响因子：
15
通讯作者：
Hayashi, T
中科院分区：
文献类型：
--
作者：
Sato, H;Watanabe, M;Hayashi, T
构建了在两个丙酸血红素侧链末端具有疏水结构域的新的重组马心肌红蛋白。通过激光闪光光解和停流快速混合技术详细检查了重构的脱氧肌红蛋白的 O2 和 CO 结合。人工创建的结构域充当了阻止外源配体渗透到血红素口袋的屏障，而结合的 O2 在重建的肌红蛋白以及天然肌红蛋白中都稳定。相反，与天然蛋白相比，重构的肌红蛋白的CO解离率增加了20倍，这表明将疏水结构域掺入到血红素口袋上扰乱了重构的肌红蛋白的远端位点结构。结果，重构肌红蛋白的显着配体选择性显着增加，有利于 O2 而非 CO，M' 值 (=KCO/KO2) 为 0.88，而据我们所知，不存在 O2 亲和力超过 CO 的肌红蛋白突变体。目前的工作得出的结论是，通过对丙酸血红素进行化学修饰，且远端位点的氨基酸残基没有任何突变，肌红蛋白相对于 CO 的 O2 选择性显着提高。
New, reconstituted horse heart myoglobins possessing a hydrophobic domain at the terminal of the two heme propionate side chains were constructed. The O2and CO bindings for the reconstituted deoxymyoglobins were examined in detail by laser flash photolysis and stopped-flow rapid mixing techniques. The artificially created domain worked as a barrier against exogenous ligand penetration into the heme pocket, whereas the bound O2was stabilized in the reconstituted myoglobin as well as in the native one. In contrast, the CO dissociation rate for the reconstituted myoglobin increased by 20-fold compared to the native protein, suggesting that the incorporation of the hydrophobic domain onto the heme pocket perturbs the distal-site structure of the reconstituted myoglobin. As a result, the substantial ligand selectivity for the reconstituted myoglobin significantly increases in favor of O2over CO with theM‘value (=KCO/KO2) of 0.88, whereas, to the best of our knowledge, there is no myoglobin mutant in which the O2affinity exceeds the CO one. The present work concludes that the O2selectivity of myoglobin over CO is markedly improved by chemically modifying the heme propionates without any mutation of the amino acid residues in the distal site.