Pearce Michael J, Arora Pooja, Festa Richard A, Butler-Wu Susan M, Gokhale Rajesh S, Darwin K Heran
Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA.
EMBO J. 2006 Nov 15;25(22):5423-32. doi: 10.1038/sj.emboj.7601405. Epub 2006 Nov 2.
The putative proteasome-associated proteins Mpa (Mycobaterium proteasomal ATPase) and PafA (proteasome accessory factor A) of the human pathogen Mycobacterium tuberculosis (Mtb) are essential for virulence and resistance to nitric oxide. However, a direct link between the proteasome protease and Mpa or PafA has never been demonstrated. Furthermore, protein degradation by bacterial proteasomes in vitro has not been accomplished, possibly due to the failure to find natural degradation substrates or other necessary proteasome co-factors. In this work, we identify the first bacterial proteasome substrates, malonyl Co-A acyl carrier protein transacylase and ketopantoate hydroxymethyltransferase, enzymes that are required for the biosynthesis of fatty acids and polyketides that are essential for the pathogenesis of Mtb. Maintenance of the physiological levels of these enzymes required Mpa and PafA in addition to proteasome protease activity. Mpa levels were also regulated in a proteasome-dependent manner. Finally, we found that a conserved tyrosine of Mpa was essential for function. Thus, these results suggest that Mpa, PafA, and the Mtb proteasome degrade bacterial proteins that are important for virulence in mice.
人类病原体结核分枝杆菌（Mtb）中假定的蛋白酶体相关蛋白Mpa（结核分枝杆菌蛋白酶体ATP酶）和PafA（蛋白酶体辅助因子A）对于毒力和对一氧化氮的抗性至关重要。然而，蛋白酶体蛋白酶与Mpa或PafA之间的直接联系从未得到证实。此外，细菌蛋白酶体在体外的蛋白质降解尚未实现，这可能是由于未能找到天然降解底物或其他必要的蛋白酶体辅助因子。在这项工作中，我们鉴定出了首批细菌蛋白酶体底物，丙二酰辅酶A酰基载体蛋白转酰基酶和酮泛酸羟甲基转移酶，它们是Mtb致病机制所必需的脂肪酸和聚酮化合物生物合成所需的酶。维持这些酶的生理水平除了需要蛋白酶体蛋白酶活性外，还需要Mpa和PafA。Mpa水平也以蛋白酶体依赖的方式受到调节。最后，我们发现Mpa中一个保守的酪氨酸对于其功能至关重要。因此，这些结果表明Mpa、PafA和Mtb蛋白酶体可降解对小鼠毒力很重要的细菌蛋白。
