LIGAND GATED TRANSPORT THROUGH FEPA

描述（改编自申请人的摘要）：细菌精细铁 螯合剂，从环境中去除铁，包括他们的人类和 动物宿主铁的获得是致病性的决定因素。 一个这样 铁螯合物，铁载体肠杆菌素，进入革兰氏阴性菌 通过外膜的FepA蛋白。 FepA是配体门控孔蛋白， 在铁肠杆菌素结合中， 跨膜孔 这种高亲和力的多特异性，多组分，能量 依赖性转运过程是原核生物膜的一个范例 生物化学 基于FepA晶体结构，所提出的研究将 使用分子生物学、生物化学和生物物理学方法来研究 铁肠杆菌素摄取的机制。 实验将解决两个问题 运输事件的各个阶段，即结合和内化。 克莱巴博士会 通过结合实验研究初始识别事件的特异性 在野生型FepA和定点突变体上， N-末端的顶部环的外部环中的残基 球状域 他将类似地描述配体内化 通过诱变靶残基的反应，所述靶残基是保守的 革兰氏阴性细菌配体门控孔蛋白。 感兴趣的突变蛋白， 那些具有受损配体结合或配体内化表型的人， 最后，他将表演 生物物理分析的构象变化发生在FepA的配体过程中， 运输

DESCRIPTION (Adapted from the Applicant's Abstract): Bacteria elaborate iron chelators that scavenge iron from the environment, including their human and animal hosts. Iron acquisition is a determinant of pathogenicity. One such iron chelate, the siderophore enterobactin, enters gram-negative bacteria through the FepA protein of the outer membrane. FepA is a ligand-gated porin, in that binding of ferric enterobactin triggers transport through its transmembrane pore. This high affinity multispecific, multicomponent, energy dependent transport process is a paradigm of prokaryotic membrane biochemistry. Based on the FepA crystal structure, the proposed research will use molecular biological, biochemical, and biophysical methods to investigate the mechanism of ferric enterobactin uptake. The experiments will address two stages of the transport event, binding and internalization. Dr. Klebba will study the specificity of the initial recognition event by binding experiments on both wild type FepA and site-directed mutants, containing alterations to residues in either the external loops of the top loops of the N-terminal globular domain. He will similarly characterize the ligand internalization reaction by mutagenesis of target residues that are conserved among other Gram-negative bacterial ligand-gated porins. Mutant proteins of interest, those with impaired ligand binding or ligand internalization phenotypes, will be crystallized and studied by X-ray diffraction Finally, he will perform biophysical analyses of conformation changes that occur in FepA during ligand transport.