Structure and Function of Heme-regulated Proteins and Their Molecular Mechanisms

血红素调节蛋白的结构、功能及其分子机制

基本信息

批准号：
15350101
负责人：
ISHIMORI Koichiro
金额：
$ 9.28万
依托单位：
Hokkaido University (2005)Kyoto University (2003-2004)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

The major results we have obtained in this research project are as follows:1. Ligation of Cys to Ferric Heme in Irr and IRP2. Based on the resonance Raman spectra, we successfully identified the Fe-Cys stretching modes in ferric heme-bound Irr and IRP2. These Fe-Cys stretching modes were downshifted, compared with that in conventional Cys-ligated hemoproteins such as P450cam. The downshifted Fe-Cys stretching modes correspond to the lower affinities of these proteins to ferric heme, which is also supported by fluorescence heme titration in Irr. Such weak affinities of these proteins to heme would be one of the characteristics of heme-regulated proteins having "Heme Regulatory Motif'2. Redox-dependent Replacement of Axial Ligands. We confirmed the ligation of Cys to ferric heme in Irr and IRP2. By reduction of the heme iron, however, the absorption spectra of heme-bound Irr and IRP2 were drastically changed and the resultant spectra were quite different from ferrous P450cam, which were rather similar to bis-His ligated hemoproteins like cytochrome b_5. The spectral similarity to His-ligated hemoprotein was more evident in the CO adducts of heme-bound Irr and IRP2. The resonance Raman measurements. clearly showed the Fe-His stretching modes in ferrous heme bound lrr and IRP2 and the Fe-C and FeC-O stretching modes in the CO adducts, confirming that axial Cys is replaced with His by reduction of the heme iron. Considering that molecular oxygen can bind to ferrous heme, not ferric heme, the His ligated species in these proteins would be active species to generate reactive oxygen species, which leads to the oxidative modification of the peptide and protein degradation.

我们在该研究项目中获得的主要结果如下：1。在IRR和IRP2中将Cys与铁血红素结合。基于共振拉曼光谱，我们成功地确定了铁蛋白血红素结合的IRR和IRP2中的Fe-cys拉伸模式。与常规的Cys绑扎的血蛋白（如P450CAM）相比，这些Fe-cys拉伸模式是降剪的。降档的Fe-cys拉伸模式对应于这些蛋白质对铁血红素的较低亲和力，这也对IRR中的荧光血红素滴定也支持。这些蛋白质与血红素的这种弱相关性将是具有“血红素调节序列2。氧化还原依赖性轴向配体的替换剂的替代蛋白质的特征之一。我们证实了Cys在IRR和IRP2中与IRP2中Cys的连接，但是通过减少了IRRP2的IRRP2。与bis-HIS相似的p450cam与细胞色素b_5相似，与触发的血液蛋白相似。 CO加合物中的模式通过减少血红素铁可以替代轴向Cys，因为分子氧可以与铁血红素结合，而不是铁血红素，这些蛋白质中的连接物种将是活性物种，可以产生反应性氧气，从而导致氧化剂的氧化蛋白质和蛋白质蛋白质。