A hemerythrin-like domain in a bacterial chemotaxis protein
A hemerythrin-like domain in a bacterial chemotaxis protein
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DOI：
10.1021/bi992796o
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发表时间：
2000-05-02
期刊：
影响因子：
2.9
通讯作者：
Sanders-Loehr, J
中科院分区：
文献类型：
--
作者：
Xiong, JJ;Kurtz, DM;Sanders-Loehr, J
Hemerythrin（Hr）是一种在一些海洋无脊椎动物中发现的携带O-2的蛋白质。所有Hrs中的保守序列基序为氧代/羟基桥接的二铁活性位点以及疏水性O-2结合口袋提供了五个组氨酸和两个羧酸配体。数据库搜索在来自厌氧硫酸盐还原菌脱硫弧菌（Desulfovibrio）的基因dcrH的3'末端定位了先前未识别的Hr样序列基序（D.）vulgaris（Hildenborough）.该基因编码一个假定的甲基接受趋化蛋白，DcrH。我们已经通过免疫印迹确定了一个全长DcrH，包括Hr样结构域，在D. vulgaris（Hildenborough）. DcrH的C-末端结构域在大肠杆菌中单独表达后，折叠成稳定的蛋白DcrH-Hr。DcrH-Hr及其叠氮加合物的紫外-可见吸收光谱和共振拉曼光谱清楚地证明了与Hr中发现的二铁（III）位点非常相似的矿石桥连二铁（III）位点。基于紫外-可见吸收光谱，还原的DcrH-Hr的暴露DcrH-Hr（无色，推测为二价铁）与空气反应生成的O-2加合物也与Hr的O-2加合物非常相似。与Hr不同，DcrH-Hr的O-2加合物在室温下几分钟内发生自动氧化。DcrH-Hr的O-2结合口袋似乎比Hr大。vulgaris和DcrH的假定趋化功能，DcrH的Hr样结构域的一个可能的作用是O-2敏感。DcrH-Hr是来自任何微生物的Hr样蛋白的第一个表征实例。
Hemerythrin(Hr) is an O-2-carrying protein found in some marine invertebrates. A conserved sequence motif in all Hrs provides five histidine and two carboxylate Ligands to an oxo-/hydroxo-bridged diiron active site, as well as a hydrophobic O-2 binding pocket. Database searches located a previously unrecognized Hr-like sequence motif at the 3' end of the gene, dcrH, from the anaerobic sulfate-reducing bacterium, Desulfovibrio (D.) vulgaris (Hildenborough). This gene encodes a putative methyl-accepting chemotaxis protein, DcrH. We have established by immunoblotting that a full-length DcrH, including the Hr-like domain, is expressed in D. vulgaris (Hildenborough). The C-terminal domain of DcrH, when expressed separately in recombinant form in Escherichia coli, was found to fold into a stable protein, DcrH-Hr. The UV-vis absorption and resonance Raman spectra of DcrH-Hr, and of its azide adduct, provide clear evidence for an ore-bridged diiron(III) site very similar to that found in Hr. Based on UV-vis absorption spectra, exposure of the reduced (colorless, presumably diferrous) DcrH-Hr to air resulted in formation of an O-2 adduct also very similar to that of Hr, Unlike that of Hr, the O-2 adduct of DcrH-Hr autoxidized within a few minutes at room temperature. The O-2 binding pocket of DcrH-Hr appears to be larger than that of Hr. Given the air-sensitive nature of D. vulgaris and the putative chemotactic function of DcrH, one possible role for the Hr-like domain of DcrH is O-2-sensing. DcrH-Hr is the first characterized example of a Hr-like protein from any microorganism.