MECHANISM OF HEME CAPTURE BY THE HEMOPHORE SECRETED BY PSEUDOMONAS AERUGINOSA

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 血红素是哺乳动物体内循环铁的最丰富来源。因此，许多病原菌，包括机会主义的铜绿假单胞菌，热衷于捕获和内化它，以克服它们在哺乳动物宿主中遇到的非常低的自由铁浓度，这就不足为奇了。为了捕获血红素，包括铜绿假单胞菌在内的几种病原菌都部署了一个血红素获取系统(HAS)，该系统由分泌到细胞外空间的蛋白质(HasAp)和外膜受体(Hasr)组成。HasAp也被称为血细胞，因为它有效地捕获血红蛋白-血红素，并将其传递给受体，以便随后内化。本文提出的研究旨在实现对蛋白质-蛋白质相互作用的基本分子水平的理解，这些相互作用使HasAp能够从人类血红蛋白中“窃取”血红素。特别是，研究人员试图对决定血红素从人类血红蛋白转移到HasAp的因素获得前所未有的结构性、动态性和机械性的见解。这一长期目标将通过追求两个主要目标来实现：1)阐明apo-HasAp的三维结构；2)确定HasAp在血红素转移之前与血红蛋白结合时形成的结合复合体的结合界面，以及破译HasAp结构元件的粗略重组在分子识别和与血红蛋白结合中所起的作用。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Heme is the most abundant source of circulating iron in mammals. It is therefore not surprising that many pathogenic bacteria, including the opportunistic Pseudomonas aeruginosa, avidly pursue its capture and internalization to overcome the very low free-iron concentrations encountered in their mammalian hosts. To capture heme, several pathogenic bacteria, including P. aeruginosa, deploy a heme acquisition system (Has), which consists of a protein secreted to the extracellular space (HasAp) and an outer membrane receptor (HasR). HasAp is also termed a hemophore because it efficiently captures hemoglobin-heme and delivers it to the receptor for subsequent internalization. The studies proposed herein aim to achieve fundamental molecular level understanding of the protein-protein interactions that allow HasAp to "steal" heme from human hemoglobin. In particular, the investigators seek to gain unprecedented structural, dynamic and mechanistic insights into the factors that determine the transfer of heme from human hemoglobin to HasAp. This long-range goal will be reached by pursuing two main objectives: 1) Elucidate the three dimensional structure of apo-HasAp, 2) Identify the binding interface of the encounter complex that forms when HasAp binds to hemoglobin, prior to heme transfer, and decipher the role played by the gross reorganization of HasAp structural elements in the molecular recognition and binding to hemoglobin.