Neya Saburo, Nagai Masako, Nagatomo Shigenori, Hoshino Tyuji, Yoneda Tomoki, Kawaguchi Akira T
Department of Physical Chemistry, Graduate School of Pharmaceutical Sciences, Chiba University, Chuoh-Inohana, Chiba City, Chiba 260-8675, Japan.
Research Center for Micro-Nano Technology, Hosei University, Koganei, Tokyo 184-0003, Japan.
Biochim Biophys Acta. 2016 May;1857(5):582-588. doi: 10.1016/j.bbabio.2015.09.009. Epub 2015 Oct 3.
Myoglobin reconstitution with various synthetic heme analogues was reviewed to follow the consequences of modified heme-globin interactions. Utility of dimethyl sulfoxide as the solvent for water-insoluble hemes was emphasized. Proton NMR spectroscopy revealed that loose heme-globin contacts in the heme pocket eventually caused the dynamic heme rotation around the iron-histidine bond. The full rotational rate was estimated to be about 1400 s(-1) at room temperature for 1,4,5,8-tetramethylhemin. The X-ray analysis of the myoglobin containing iron porphine, the smallest heme without any side chains, showed that the original globin fold was well conserved despite the serious disruption of native heme-globin contacts. Comparison between the two myoglobins with static and rotatory prosthetic groups indicated that the oxygen and carbon monoxide binding profiles were almost unaffected by the heme motion. On the other hand, altered tetrapyrrole array of porphyrin dramatically changed the dissociation constant of oxygen from 0.0005 mm Hg of porphycene-myoglobin to ∞ in oxypyriporphyrin-myoglobin. Heme-globin interactions in myoglobin were also monitored with circular dichroism spectroscopy. The observation on several reconstituted protein revealed an unrecognized role of the propionate groups in protoheme. Shortening of heme 6,7-propionates to carboxylates resulted in almost complete disappearance of the positive circular dichroism band in the Soret region. The theoretical analysis suggested that the disappeared circular dichroism band reflected the cancellation effects between different conformers of the carboxyl groups directly attached to heme periphery. The above techniques were proposed to be applicable to other hemoproteins to create new biocatalysts. This article is part of a Special Issue entitled Biodesign for Bioenergetics--the design and engineering of electronic transfer cofactors, proteins and protein networks, edited by Ronald L. Koder and J.L. Ross Anderson.
对肌红蛋白与各种合成血红素类似物的重组进行了综述，以追踪血红素-珠蛋白相互作用改变的后果。强调了二甲基亚砜作为水不溶性血红素溶剂的实用性。质子核磁共振光谱显示，血红素口袋中松散的血红素-珠蛋白接触最终导致血红素围绕铁-组氨酸键进行动态旋转。对于1,4,5,8-四甲基血红素，在室温下其完整的旋转速率估计约为1400 s(-1)。对含有铁卟啉（最小的无任何侧链的血红素）的肌红蛋白的X射线分析表明，尽管天然血红素-珠蛋白接触受到严重破坏，但原始的珠蛋白折叠结构仍得到很好的保留。对具有静态和旋转辅基的两种肌红蛋白的比较表明，血红素运动几乎不影响氧气和一氧化碳的结合曲线。另一方面，卟啉的四吡咯阵列改变极大地改变了氧气的解离常数，从卟吩-肌红蛋白的0.0005 mmHg变为氧化吡啶卟啉-肌红蛋白中的无穷大。还通过圆二色光谱监测了肌红蛋白中的血红素-珠蛋白相互作用。对几种重组蛋白的观察揭示了原血红素中丙酸基团的一个未被认识的作用。将血红素6,7-丙酸酯缩短为羧酸盐导致Soret区域的正圆二色带几乎完全消失。理论分析表明，消失的圆二色带反映了直接连接到血红素周边的羧基不同构象之间的抵消作用。上述技术被认为适用于其他血红蛋白，以创造新的生物催化剂。本文是名为“生物能量学的生物设计——电子传递辅因子、蛋白质和蛋白质网络的设计与工程”的特刊的一部分，由罗纳德·L·科德和J.L.罗斯·安德森编辑。
