Zinc dependent conformational changes in AdcR and their impact on DNA binding

肺炎链球菌是一种革兰氏阳性、兼性厌氧菌，在上呼吸道定植 大多数人的身体。病原体如S.肺炎依靠宿主提供生长所需的所有营养， 包括几种过渡金属离子。锌离子是所有生命系统所需的微量营养素。细胞内 Zn ~（2+）在S. pneumoniae的表达受两种转录因子（TF）的调控。这些蛋白质称为AdcR， 已知SczA以高亲和力结合Zn 2+离子。在这两种蛋白质中，锌（II）结合事件诱导了结构上的 蛋白质的变化，使这些Zn-TF对其特异性DNA启动子的亲和力显著增加 地区正是这个过程调节了一系列负责S内Zn 2+稳态的蛋白。肺炎。 Zn 2+、TF和DNA之间的化学平衡是治疗剂开发的有吸引力的靶标，其中 影响S。肺炎菌适应宿主内新位置的能力可直接影响其毒力。 AdcR在其金属结合结构域中结合两个Zn 2+离子，并且该结合位点通过一系列的免疫调节来稳定。 蛋白质中非结构化环之间的分子内相互作用。具体地，位点1是配位的 饱和四面体位点，其中所有四个位置通过氨基酸侧链残基配位。站点2也 采用四面体配位模式，然而这些位点之一被水分子占据，这提供了 破坏这个系统的机会与该提议相关的中心假设是，锌（II）结合 诱导AdcR中动态环的组织（Lys 22至Ser 38），其将蛋白质锁定到有利的DNA中 结合构象通过突变（aim 1）或化学试剂（aim 2）对该环的结构进行扰动， 影响Zn 2AdcR结构，导致Zn 2AdcR/DNA结合的热力学变化。

Streptococcus pneumoniae is a Gram-positive, facultative anaerobic bacteria that colonizes in the upper respiratory tract of most humans. Pathogens like S. pneumoniae rely on their host to provide all nutrients for growth, which includes several transition metal ions. Zinc(II) ions are required micronutrients for all living systems. The intracellular Zn2+ concentration in S. pneumoniae is regulated by two transcription factors (TFs). These proteins, termed AdcR and SczA, are known to bind Zn2+ ions with high affinity. In both proteins, the zinc(II) binding events induce a structural change in the protein that affords a dramatic increase in the affinity of these Zn-TFs for their specific DNA promotor regions. It is this process that regulates a series of proteins responsible for Zn2+ homeostasis within S. pneumoniae. The chemical equilibria between Zn2+, TFs, and DNA are attractive targets for therapeutic agent development, where impacting S. pneumoniae’s ability to adapt to new locations within a host can directly impact its virulence. AdcR binds two Zn2+ ions in its metal binding domain, and this binding site is stabilized through a series of intramolecular interactions between an unstructured loop in the protein. Specifically, site 1 is a coordinatively saturated tetrahedral site, where all four positions are coordinated through amino-acid side chain residues. Site 2 also adopts a tetrahedral coordination mode, however one of these sites is occupied by a water molecule, which provides an opportunity to disrupt this system. The central hypothesis associated with this proposal is that zinc(II) binding induces an organization of a dynamic loop in AdcR (Lys22 to Ser38), which locks the protein into a favorable DNA binding conformation. Perturbations to the structure of this loop by mutation (aim 1) or chemical agents (aim 2) can impact the Zn2AdcR structure significantly leading to changes in the thermodynamics of Zn2AdcR/DNA binding.