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Abstract：
The cell wall of mycobacteria plays a key role in interactions with the environment. Its ability to act as a selective filter is crucial to bacterial survival. Proteins in the cell wall enable this function by mediating the import and export of diverse metabolites, from ions to lipids to proteins. Identifying cell wall proteins is an important step in assigning function, especially as many mycobacterial proteins lack functionally characterized homologues. Current methods for protein localization have inherent limitations that reduce accuracy. Here we showed that although chemical labeling of live cells did not exclusively label surface proteins, protein tagging by the engineered peroxidase APEX2 within live Mycobacterium tuberculosis accurately identified the cytosolic and cell wall proteomes. Our data indicate that substrates of the virulence-associated Type VII ESX secretion system are exposed to the periplasm, providing insight into the currently unknown mechanism by which these proteins cross the mycobacterial cell envelope.
摘要：
分枝杆菌的细胞壁在与环境的相互作用中起关键作用。它作为选择性过滤器的能力对细菌存活至关重要。细胞壁中的蛋白质通过介导各种代谢物的导入和导出来实现这种功能，从离子到脂质再到蛋白质。鉴定细胞壁蛋白是分配功能的重要步骤，尤其是许多分枝杆菌蛋白缺乏功能特征的同源物。目前用于蛋白质定位的方法具有降低准确性的固有限制。在这里，我们发现尽管活细胞的化学标记并不完全标记表面蛋白，活结核分枝杆菌内的工程化过氧化物酶APEX2的蛋白质标记准确地鉴定了细胞溶质和细胞壁蛋白质组。我们的数据表明，毒力相关的VII型ESX分泌系统的底物暴露于周质，提供对这些蛋白质穿过分枝杆菌细胞包膜的当前未知机制的见解。
