Crystal Structure of the Iron-dependent Regulator from Mycobacterium tuberculosis at 2.0-Å Resolution Reveals the Src Homology Domain 3-like Fold and Metal Binding Function of the Third Domain*-猫眼课题宝

结核分枝杆菌铁依赖性调节因子的晶体结构（2.0-Å 分辨率）揭示了 Src 同源结构域 3 状折叠和第三结构域的金属结合功能*

DOI：

发表时间：

2000

期刊：

Journal of Biological Chemistry

影响因子：

4.8

通讯作者：

中科院分区：

生物学2区

文献类型：

作者：

M. Feese;B. P. Ingason;J. Goranson;R. Holmes;W. Hol

铁依赖性调节因子是毒力因子和铁清除系统的主要转录调节因子，对几种细菌病原体的感染很重要。在这里，我们展示了来自结核分枝杆菌的野生型铁依赖性调节因子的2.0-γ晶体结构，其处于完全活性的全抑制子构象。明确的，公正的电子密度Src同源结构域3样的第三个域，这往往是不可见的结构中的铁依赖性监管机构，揭示了密度修饰和平均。该结构域是细菌蛋白中Src同源结构域3样折叠的罕见实例之一，此外，通过向金属位点1处的五配位钴原子贡献两个配体（一个Glu和一个Gln）来显示金属结合功能。两个金属位点都被完全占据，并且在金属位点1（“水1”）和金属位点2（“水2”）处紧密结合的水分子被明确地识别。Leu 4的主链羰基通过水2与金属位点2的钴原子间接相互作用，相邻的残基Val 5形成罕见的γ转角。残基1-3是有序的，并产生许多相互作用。因此，这些有序的溶剂分子和N-末端五肽的构象和相互作用可能是重要的金属依赖性激活。

Iron-dependent regulators are primary transcriptional regulators of virulence factors and iron scavenging systems that are important for infection by several bacterial pathogens. Here we present the 2.0-Å crystal structure of the wild type iron-dependent regulator from Mycobacterium tuberculosis in its fully active holorepressor conformation. Clear, unbiased electron density for the Src homology domain 3-like third domain, which is often invisible in structures of iron-dependent regulators, was revealed by density modification and averaging. This domain is one of the rare examples of Src homology domain 3-like folds in bacterial proteins, and, in addition, displays a metal binding function by contributing two ligands, one Glu and one Gln, to the pentacoordinated cobalt atom at metal site 1. Both metal sites are fully occupied, and tightly bound water molecules at metal site 1 (“Water 1”) and metal site 2 (“Water 2”) are identified unambiguously. The main chain carbonyl of Leu4 makes an indirect interaction with the cobalt atom at metal site 2 via Water 2, and the adjacent residue, Val5, forms a rare γ turn. Residues 1–3 are well ordered and make numerous interactions. These ordered solvent molecules and the conformation and interactions of the N-terminal pentapeptide thus might be important in metal-dependent activation.