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首页> 外文期刊>Biochimica et Biophysica Acta. General Subjects >Spectroscopic evidence for a 5-coordinate oxygenic ligated high spin ferric heme moiety in the Neisseria meningitidis hemoglobin binding receptor
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Spectroscopic evidence for a 5-coordinate oxygenic ligated high spin ferric heme moiety in the Neisseria meningitidis hemoglobin binding receptor

机译：在脑膜炎奈瑟氏球菌血红蛋白结合受体中有5个配位的氧连接的高自旋铁血红素部分的光谱证据

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Background For many pathogenic microorganisms, iron acquisition represents a significant stress during the colonization of a mammalian host. Heme is the single most abundant source of soluble iron in this environment. While the importance of iron assimilation for nearly all organisms is clear, the mechanisms by which heme is acquired and utilized by many bacterial pathogens, even those most commonly found at sites of infection, remain poorly understood. Methods An alternative protocol for the production and purification of the outer membrane hemoglobin receptor (HmbR) from the pathogen Neisseria meningitidis has facilitated a biophysical characterization of this outer membrane transporter by electronic absorption, circular dichroism, electron paramagnetic resonance, and resonance Raman techniques. Results HmbR co-purifies with 5-coordinate high spin ferric heme bound. The heme binding site accommodates exogenous imidazole as a sixth ligand, which results in a 6-coordinate, low-spin ferric species. Both the 5- and 6-coordinate complexes are reduced by sodium hydrosulfite. Four HmbR variants with a modest decrease in binding efficiency for heme have been identified (H87C, H280A, Y282A, and Y456C). These findings are consistent with an emerging paradigm wherein the ferric iron center of bound heme is coordinated by a tyrosine ligand. Conclusion In summary, this study provides the first spectroscopic characterization for any heme or iron transporter in Neisseria meningitidis, and suggests a coordination environment heretofore unobserved in a TonB-dependent hemin transporter. General Significance A detailed understanding of the nutrient acquisition pathways in common pathogens such as N. meningitidis provides a foundation for new antimicrobial strategies.
机译：背景技术对于许多病原微生物，铁的捕获代表着哺乳动物宿主定殖期间的巨大压力。血红素是这种环境中唯一最丰富的可溶性铁来源。尽管铁同化对几乎所有生物的重要性都很明确，但对许多细菌病原体（甚至是在感染部位最常见的病原体）获取和利用血红素的机制仍知之甚少。方法从病原体脑膜炎奈瑟氏球菌生产和纯化外膜血红蛋白受体（HmbR）的替代方案已通过电子吸收，圆二色性，电子顺磁共振和共振拉曼技术促进了该外膜转运蛋白的生物物理表征。结果HmbR与5坐标高自旋三价铁血红素结合共纯化。血红素结合位点容纳作为第六配体的外源咪唑，这导致六配位，低旋转的铁物种。亚硫酸氢钠可还原5位和6位配合物。已经鉴定出四种与血红素结合效率适度降低的HmbR变体（H87C，H280A，Y282A和Y456C）。这些发现与新兴的范例相一致，其中结合的血红素的三价铁中心由酪氨酸配体配位。结论总之，本研究为脑膜炎奈瑟氏球菌中任何血红素或铁转运蛋白提供了第一个光谱学表征，并提出了迄今为止在依赖于TonB的血红素转运蛋白中尚未观察到的协调环境。一般意义对常见病原体（例如脑膜炎奈瑟菌）的营养获取途径的详细了解为新的抗菌策略提供了基础。

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