Raju Ravikiran M, Jedrychowski Mark P, Wei Jun-Rong, Pinkham Jessica T, Park Annie S, O'Brien Kathryn, Rehren German, Schnappinger Dirk, Gygi Steven P, Rubin Eric J
Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, United States of America.
Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, United States of America.
PLoS Pathog. 2014 Mar 6;10(3):e1003994. doi: 10.1371/journal.ppat.1003994. eCollection 2014 Mar.
Unlike most bacterial species, Mycobacterium tuberculosis depends on the Clp proteolysis system for survival even in in vitro conditions. We hypothesized that Clp is required for the physiologic turnover of mycobacterial proteins whose accumulation is deleterious to bacterial growth and survival. To identify cellular substrates, we employed quantitative proteomics and transcriptomics to identify the set of proteins that accumulated upon the loss of functional Clp protease. Among the set of potential Clp substrates uncovered, we were able to unambiguously identify WhiB1, an essential transcriptional repressor capable of auto-repression, as a substrate of the mycobacterial Clp protease. Dysregulation of WhiB1 turnover had a toxic effect that was not rescued by repression of whiB1 transcription. Thus, under normal growth conditions, Clp protease is the predominant regulatory check on the levels of potentially toxic cellular proteins. Our findings add to the growing evidence of how post-translational regulation plays a critical role in the regulation of bacterial physiology.
与大多数细菌种类不同，结核分枝杆菌即使在体外条件下生存也依赖于Clp蛋白酶解系统。我们推测，Clp对于结核分枝杆菌蛋白质的生理性周转是必需的，这些蛋白质的积累对细菌生长和存活有害。为了鉴定细胞底物，我们采用定量蛋白质组学和转录组学来鉴定在功能性Clp蛋白酶缺失时积累的蛋白质组。在发现的一组潜在Clp底物中，我们能够明确鉴定出WhiB1，一种能够自我抑制的必需转录阻遏物，作为结核分枝杆菌Clp蛋白酶的底物。WhiB1周转的失调具有毒性作用，这种作用不能通过抑制whiB1转录来挽救。因此，在正常生长条件下，Clp蛋白酶是对潜在有毒细胞蛋白水平的主要调节控制。我们的发现进一步证明了翻译后调控在细菌生理学调节中如何发挥关键作用。
