Ligand binding properties of myoglobin reconstituted with iron porphycene:: Unusual O2 binding selectivity against CO binding
Ligand binding properties of myoglobin reconstituted with iron porphycene:: Unusual O2 binding selectivity against CO binding
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DOI：
10.1021/ja045880m
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发表时间：
2004-12-15
影响因子：
15
通讯作者：
Hayashi, T
中科院分区：
文献类型：
--
作者：
Matsuo, T;Dejima, H;Hayashi, T
摘要抹香鲸肌红蛋白是一种储氧型血红蛋白，它与含有两个丙酸酯的铁卟啉2，7-diethyl-3，6，12，17-tetramethyl-13，16-bis(carboxyethyl)porphycenatoiron.重组成功。对重组肌红蛋白的理化性质和配体结合进行了研究。重组肌红蛋白对酸变性表现出显着的稳定性，EPR谱仅表现出低自旋特征。光谱电化学法测定的Fe(III)/Fe(II)氧化还原电位(-190 mV vs NHE)远低于野生型。这些结果可以归因于His93与卟啉铁的强烈配位，这是由卟烯环对称性的性质引起的。亚铁重组肌红蛋白的O2亲和力是野生型的2600倍，这主要是由于O-2解离速率的降低，而CO亲和力并没有显著提高。结果，重组肌红蛋白的02亲和力超过其CO亲和力(M‘=K-CO/K-O2<；1)。对H64A突变体的配体结合研究支持重组肌红蛋白02的缓慢解离主要是由于Fe-O-2 sigma键的稳定所致。重组肌红蛋白的一氧化碳(CO)络合物的红外光谱表明，Fe-C-0键有几种结构和/或静电构象，但这与CO解离速率没有直接关系。肌红蛋白与铁卟啉的高O-2亲和力和独特的特性表明，与合成的血红素重组不仅是了解肌红蛋白的生理功能，而且还可以在蛋白质上产生量身定制的功能。
Sperm whale myoglobin, an oxygen storage hemoprotein, was successfully reconstituted with the iron porphycene having two propionates, 2,7-diethyl-3,6,12,17-tetramethyl-13,16-bis(carboxyethyl)porphycenatoiron. The physicochemical properties and ligand bindings of the reconstituted myoglobin were investigated. The ferric reconstituted myoglobin shows the remarkable stability against acid denaturation and only a low-spin characteristic in its EPR spectrum. The Fe(III)/Fe(II) redox potential (-190 mV vs NHE) determined by the spectroelectrochernical measurements was much lower than that of the wildtype. These results can be attributed to the strong coordination of His93 to the porphycene iron, which is induced by the nature of the porphycene ring symmetry. The 02 affinity of the ferrous reconstituted myoglobin is 2600-fold higher than that of the wild-type, mainly due to the decrease in the O-2 dissociation rate, whereas the CO affinity is not so significantly enhanced. As a result, the 02 affinity of the reconstituted myoglobin exceeds its CO affinity (M' = K-CO/K-O2 < 1). The ligand binding studies on H64A mutants support the fact that the Slow 02 dissociation of the reconstituted myoglobin is primarily caused by the stabilization of the Fe-O-2 sigma-bonding. The IR spectra for the carbon monoxide (CO) complex of the reconstituted myoglobin suggest several structural and/or electrostatic conformations of the Fe-C-0 bond, but this is not directly correlated with the CO dissociation rate. The high O-2 affinity and the unique characteristics of the myoglobin with the iron porphycene indicate that reconstitution with a synthesized heme is a useful method not only to understand the physiological function of myoglobin but also to create a tailor-made function on the protein.