Characterization of a Mycobacterium tuberculosis Nanocompartment and Its Potential Cargo Proteins
Characterization of a Mycobacterium tuberculosis Nanocompartment and Its Potential Cargo Proteins
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DOI：
10.1074/jbc.m114.570119
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发表时间：
2014-06-27
影响因子：
4.8
通讯作者：
Goulding, Celia W.
中科院分区：
文献类型：
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作者：
Contreras, Heidi;Joens, Matthew S.;Goulding, Celia W.
结核分枝杆菌已经进化出各种机制，通过这些机制，细菌可以在宿主免疫反应产生的许多环境攻击下保持体内平衡。M.结核病携带参与氧化应激反应的酶，所述酶在活化的巨噬细胞中产生活性氧物质期间帮助存活。先前的研究表明，染料脱色过氧化物酶（DyP）被细菌纳米区室，Ekenin（Enc）封装，其中包装的DyP通过独特的C-末端延伸与Enc相互作用。M.结核病还在与M.结核病DyP（Mt-DyP），其含有C-末端延伸。总之，这些观察结果表明Mt-DyP与Mt-Enc相互作用。此外，有人建议，DyPs可以作为血红素依赖性过氧化物酶或脱铁螯合酶。如Mt-DyP，M.结核铁储存铁蛋白Mt-BfrB和结核分枝杆菌M.参与叶酸生物合成的结核蛋白7，8-二氢新蝶呤醛缩酶（Mt-FolB）具有也可与Mt-Enc相互作用的C-末端尾。这是第一次，我们通过共纯化和电子显微镜显示，分枝杆菌通过Mt-Enc可以封装Mt-DyP，Mt-BfrB和Mt-FolB。游离或包封的蛋白质的功能研究表明，它们在Mt-Enc纳米区室中保留了其酶活性。Mt-DyP、Mt-FolB和Mt-BfrB都具有抗氧化特性，这表明如果这些蛋白质被Mt-Enc包裹，那么这种纳米笼可能在M.结核氧化应激反应这份报告提供了初步的结构和生化线索的分子机制，利用区室化的分枝杆菌细胞可能有助于当地环境的解毒，以确保长期生存。
Mycobacterium tuberculosis has evolved various mechanisms by which the bacterium can maintain homeostasis under numerous environmental assaults generated by the host immune response. M. tuberculosis harbors enzymes involved in the oxidative stress response that aid in survival during the production of reactive oxygen species in activated macrophages. Previous studies have shown that a dye-decolorizing peroxidase (DyP) is encapsulated by a bacterial nanocompartment, encapsulin (Enc), whereby packaged DyP interacts with Enc via a unique C-terminal extension. M. tuberculosis also harbors an encapsulin homolog (CFP-29, Mt-Enc), within an operon with M. tuberculosis DyP (Mt-DyP), which contains a C-terminal extension. Together these observations suggest that Mt-DyP interacts with Mt-Enc. Furthermore, it has been suggested that DyPs may function as either a heme-dependent peroxidase or a deferrochelatase. Like Mt-DyP, M. tuberculosis iron storage ferritin protein, Mt-BfrB, and an M. tuberculosis protein involved in folate biosynthesis, 7,8-dihydroneopterin aldolase (Mt-FolB), have C-terminal tails that could also interact with Mt-Enc. For the first time, we show by co-purification and electron microscopy that mycobacteria via Mt-Enc can encapsulate Mt-DyP, Mt-BfrB, and Mt-FolB. Functional studies of free or encapsulated proteins demonstrate that they retain their enzymatic activity within the Mt-Enc nanocompartment. Mt-DyP, Mt-FolB, and Mt-BfrB all have antioxidant properties, suggesting that if these proteins are encapsulated by Mt-Enc, then this nanocage may play a role in the M. tuberculosis oxidative stress response. This report provides initial structural and biochemical clues regarding the molecular mechanisms that utilize compartmentalization by which the mycobacterial cell may aid in detoxification of the local environment to ensure long term survival.