Intermolecular interactions in the AhpC/AhpD antioxidant defense system of Mycobacterium tuberculosis
Intermolecular interactions in the AhpC/AhpD antioxidant defense system of Mycobacterium tuberculosis
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DOI：
10.1016/j.abb.2004.04.017
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发表时间：
2004-07-01
影响因子：
3.9
通讯作者：
de Montellano, PRO
中科院分区：
文献类型：
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作者：
Koshkin, A;Knudsen, GM;de Montellano, PRO
结核分枝杆菌的AhpC/AhpD系统提供重要的抗氧化保护，特别是当KatG过氧化氢酶-过氧化物酶活性被抑制时，如在许多异烟肼耐药菌株中一样。在硫辛酰胺或牛二氢硫辛酰胺脱氢酶（DHLDH）的情况下，当AhpC和AhpD的混合物暴露于过氧化物时，形成正常催化系统、共价二聚体、四聚体和六聚体的组分。每种低聚物含有等摩尔量的AhpC和AhpD。这种低聚反应是可逆的，因为低聚物可以被二硫苏糖醇完全还原为单体物质。使用诱变，我们在此确认，AhpC的Cys 61和Cys 174以及AhpD的Cys 133和Cys 30对于由AhpC、AhpD、硫辛酰胺、DHLDH和NADH组成的完全重构系统中的活性是关键的。还原型AhpD还原氧化型AhpC的关键步骤是在AhpC的Cys 61和AhpD的Cys 133之间形成二硫键交联。这种交联可以通过与AhpC的Cys 174或AhpD的Cys 130的分子内反应来减少。Cys 176也可以在一定程度上取代Cys 174，提供一种冗余措施，有助于维持这种抗氧化保护系统的效率。(C)2004年爱思唯尔公司All rights reserved.
The AhpC/AhpD system of Mycobacterium tuberculosis provides important antioxidant protection, particularly when the KatG catalase-peroxidase activity is depressed, as it is in many isoniazid resistant strains. In the absence of lipoamide or bovine dihydrolipoamide dehydrogenase (DHLDH), components of the normal catalytic system, covalent dimers, tetramers, and hexamers are formed when a mixture of AhpC and AhpD is exposed to peroxide. Each of the oligomers contains equimolar amounts of AhpC and AhpD. This oligomerization is reversible because the oligomers can be fully reduced to the monomeric species by dithiothreitol. Using mutagenesis, we confirm here that Cys61 and Cys174 of AhpC as well as Cys133 and Cyst 30 of AhpD are critical for activity in the fully reconstituted system consisting of AhpC, AhpD, lipoamide, DHLDH, and NADH. A key step in the reduction of oxidized AhpC by reduced AhpD is formation of a disulfide cross-link between Cys61 of AhpC and Cys133 of AhpD. This crosslink can be reduced by intramolecular reaction with either Cys174 of AhpC or Cys130 of AhpD. Cys 176 can also, to some extent, substitute for Cys174, providing a measure of redundancy that helps to maintain the efficiency of this antioxidant protective system. (C) 2004 Elsevier Inc. All rights reserved.