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的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目及 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 血红素是哺乳动物体内最丰富的循环铁来源。因此，许多致病细菌，包括机会性铜绿假单胞菌，热切地追求其捕获和内化，以克服在其哺乳动物宿主中遇到的非常低的游离铁浓度，这并不奇怪。为了捕获血红素，包括铜绿假单胞菌在内的几种病原菌部署了血红素获取系统（Has），其由分泌到细胞外空间的蛋白质（HasAp）和外膜受体（HasR）组成。HasAp也被称为血载体，因为它有效地捕获血红蛋白-血红素并将其递送至受体用于随后的内化。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，这种相互作用允许HasAp从人类血红蛋白中“窃取”血红素。特别是，研究人员试图获得前所未有的结构，动态和机制的见解，以确定血红素从人类血红蛋白转移到HasAp的因素。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）在血红素转移之前，识别HasAp与血红蛋白结合时形成的相遇复合物的结合界面，并破译HasAp结构元件的总体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.