Catalase-peroxidase KatG of Burkholderia pseudomallei at 1.7 A resolution
Catalase-peroxidase KatG of Burkholderia pseudomallei at 1.7 A resolution
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DOI：
10.1016/s0022-2836(03)00122-0
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发表时间：
2003-03-21
影响因子：
5.6
通讯作者：
Fita, I
中科院分区：
文献类型：
--
作者：
Carpena, X;Loprasert, S;Fita, I
类鼻疽伯克霍尔德氏菌katG编码的过氧化氢酶-过氧化物酶（BpKatG）与结核分枝杆菌的KatG有65%的相同性，后者是负责激活异烟肼作为抗生素的酶。B KatG与一个未鉴定的配体的复合物的结构已被确定。使用从用液氮快速冷却的晶体中收集的X射线同步加速器数据，以1.7埃的分辨率求解和精炼p。晶体学一致因子R和R-free分别为15.3%和18.6%。结晶的酶是一个二聚体，每个亚基有一个修饰的血红素基团和一个金属离子，可能是钠。血红素基团上的修饰涉及将两个或三个原子（可能是过羟基基团）共价加成到环1上的乙烯基的仲碳原子上。添加的基团可以与两个水分子形成氢键，这两个水分子也与活性位点残基Trp 111和His 112接触，这表明该修饰可能具有催化作用。血红素修饰非常接近Trp 111、Tyr 238和Met 264侧链之间的不寻常共价加合物。此外，Trp 111似乎被氧化的吲哚环的C-δ 1。主通道，提供访问的底物过氧化氢的血红素，包含一个区域的未分配的电子密度与吡啶核苷酸样分子的结合一致。一个内部空腔，含有钠离子和一个额外的区域的未分配的密度，是明显的加合物附近，并通过第二个漏斗形通道可访问外部。一个大的裂缝在一侧的亚基是显而易见的，可能是一个潜在的底物结合位点，通过加合物的电子转移到活性位点血红素基团的明确途径。(C)2003爱思唯尔科技有限公司版权所有。
The catalase-peroxidase encoded by katG of Burkholderia pseudomallei (BpKatG) is 65% identical with KatG of Mycobacterium tuberculosis, the enzyme responsible for the activation of isoniazid as an antibiotic. The structure of a complex of B KatG with an unidentified ligand, has been. p solved and refined at 1.7 Angstrom resolution using X-ray synchrotron data collected from crystals flash-cooled with liquid nitrogen. The crystallographic agreement factors R and R-free are 15.3% and 18.6%, respectively. The crystallized enzyme is a dimer with one modified heme group and one metal ion, likely sodium, per subunit. The modification on the heme group involves the covalent addition of two or three atoms, likely a perhydroxy group, to the secondary carbon atom of the vinyl group on ring 1. The added group can form hydrogen bonds with two water molecules that are also in contact with the active-site residues Trp111 and His112, suggesting that the modification may have a catalytic role. The heme modification is in close proximity to an unusual covalent adduct among the side-chains of Trp111, Tyr238 and Met264. In addition, Trp111 appears to be oxidized on C-delta1 of the indole ring. The main channel, providing access of substrate hydrogen peroxide to the heme, contains a region of unassigned electron density consistent with the binding of a pyridine nucleotide-like molecule. An interior cavity, containing the sodium ion and an additional region of unassigned density, is evident adjacent to the adduct and is accessible to the outside through a second funnel-shaped channel. A large cleft in the side of the subunit is evident and may be a potential substrate-binding site with a clear pathway for electron transfer to the active-site heme group through the adduct. (C) 2003 Elsevier Science Ltd. All rights reserved.