Fourier transform infrared evidence for connectivity between CuB and glutamic acid 286 in cytochrome bo3 from Escherichia coli.
Fourier transform infrared evidence for connectivity between CuB and glutamic acid 286 in cytochrome bo3 from Escherichia coli.
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大肠杆菌细胞色素 bo3 中 CuB 和谷氨酸 286 之间连接的傅里叶变换红外证据。
DOI：
10.1021/bi971091o
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Woodruff,WH
中科院分区：
文献类型：
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作者：
Puustinen,A;Bailey,JA;Dyer,RB;Mecklenburg,SL;Wikstrom,M;Woodruff,WH
完全还原的一氧化碳细胞色素3的光解离导致一氧化碳（C & O）从血红素铁超快转移到双核部位的Cu上。在低温下，C ↓ [2] O与Cu ↓ [3] B结合的时间较长。在这里，我们表明，结合的C2 O到CuBperturbs的IR拉伸的非离子化的羧酸残基，这是确定为Glu 286突变为天冬氨酸或半胱氨酸。在光解离之前，该羧酸残基的羰基（CO）伸缩频率对于Glu 286为1726 cm-1，对于Glu 286 Asp为1759 cm-1。这些频率是未电离的R-COOH的明确证据，并表明羧酸是氢键键合的，尽管在Glu 286中更广泛。在Glu 286 Cys中，这种IR特征完全丧失。我们归因于在CO红外光谱的频移的结合光解的C2 O的CuB，这是中继到286位点的影响。相反，CuB−CO的2065 cm-1 C → O延伸明显受到这两种突变的影响。这些效应归因于CuB的刘易斯酸性的变化，或由C2 O取代CuB组氨酸配体。C2 O与CuB的结合也会导致IR谱带的下移，这可能是由于在3140 cm-1处的芳香族C-H伸缩，可能是组氨酸咪唑。结果表明，一个很容易极化，通过债券之间的连接组氨酸CuBligands和羧基的Glu 286。结合水分子的链可以提供这样的连接，这在血红素-铜氧化酶的质子泵机制的上下文中是感兴趣的。
Photodissociation of fully reduced, carbonmonoxy cytochromebo3causes ultrafast transfer of carbon monoxide (C⋮O) from heme iron to CuBin the binuclear site. At low temperatures, the C⋮O remains bound to CuBfor extended times. Here, we show that the binding of C⋮O to CuBperturbs the IR stretch of an un-ionized carboxylic acid residue, which is identified as Glu286 by mutation to Asp or to Cys. Before photodissociation, the carbonyl (CO)-stretching frequency of this carboxylic acid residue is 1726 cm-1for Glu286 and 1759 cm-1for Glu286Asp. These frequencies are definitive evidence for un-ionized R-COOH and suggest that the carboxylic acids are hydrogen-bonded, though more extensively in Glu286. In Glu286Cys, this IR feature is lost altogether. We ascribe the frequency shifts in the CO IR absorptions to the effects of binding photodissociated C⋮O to CuB, which are relayed to the 286 locus. Conversely, the 2065 cm-1C⋮O stretch of CuB−CO is markedly affected by both mutations. These effects are ascribed to changes in the Lewis acidity of CuB, or to displacement of a CuBhistidine ligand by C⋮O. C⋮O binding to CuBalso induces a downshift of an IR band which can be attributed to an aromatic C−H stretch, possibly of histidine imidazole, at about 3140 cm-1. The results suggest an easily polarizable, through-bond connectivity between one of the histidine CuBligands and the carboxylic group of Glu286. A chain of bound water molecules may provide such a connection, which is of interest in the context of the proton pump mechanism of the heme-copper oxidases.