Li Kunhua, Bruner Steven D
Department of Chemistry, University of Florida, Gainesville, Florida, 32611.
Proteins. 2016 Jan;84(1):118-28. doi: 10.1002/prot.24959. Epub 2015 Nov 26.
Iron acquisition is a complex, multicomponent process critical for most organisms' survival and virulence. Small iron chelating molecules, siderophores, mediate transport as key components of common pathways for iron assimilation in many microorganisms. The chemistry and biology of the extraordinary tight and specific metal binding siderophores is of general interest in terms of host/guest chemistry and is a potential target toward the development of therapeutic treatments for microbial virulence. The siderophore pathway of the moderate thermophile, Thermobifida fusca, is an excellent model system to study the process in Gram-positive bacteria. Here we describe the structure and characterization of the siderophore periplasmic binding protein, FscJ from the fuscachelin gene cluster of T. fusca. The structure shows a di-domain arrangement connected with a long α-helix hinge. Several X-ray structures detail ligand-free conformational changes at different pH values, illustrating complex interdomain flexibility of the siderophore receptors. We demonstrated that FscJ has a unique recognition mechanism and details the binding interaction with ferric-fuscachelin A through ITC and docking analysis. The presented work provides a structural basis for the complex molecular mechanisms of siderophore recognition and transportation.
铁的获取是一个复杂的多组分过程，对大多数生物体的生存和致病性至关重要。小的铁螯合分子（铁载体）作为许多微生物中铁同化常见途径的关键组分介导运输。非凡紧密且特异性的金属结合铁载体的化学和生物学在主客体化学方面具有普遍意义，并且是开发针对微生物致病性治疗方法的潜在靶点。中度嗜热菌嗜热栖热放线菌的铁载体途径是研究革兰氏阳性菌中该过程的一个优秀模型系统。在此，我们描述了嗜热栖热放线菌fuscachelin基因簇中铁载体周质结合蛋白FscJ的结构与特性。该结构呈现出由一个长α螺旋铰链连接的双结构域排列。几个X射线结构详细说明了在不同pH值下无配体的构象变化，阐明了铁载体受体复杂的结构域间灵活性。我们证明FscJ具有独特的识别机制，并通过等温滴定量热法和对接分析详细说明了与铁 - fuscachelin A的结合相互作用。所展示的工作为铁载体识别和运输的复杂分子机制提供了结构基础。
