致病性大腸桿菌引起許多傳染病，如新生兒腦膜炎，尿路感染和腸胃炎。然而，抗藥性菌株的快速出現，增加了治療此類細菌感染的難度。因此，發展新型的抗菌策略已成為最迫切的事情。幫助致病菌感染的毒力因子將是開發新型抗菌策略的潛在目標。大腸桿菌週質蛋白酶Prc的缺失會降低細菌的移動能力，而細菌的移動能力被認為是一種毒力因子，所以了解Prc蛋白酶影響細菌移動能力的機制可能有助於發展新穎的抗菌策略。因為Prc是一種蛋白酶，所以prc基因缺失菌株的移動能力下降可能是Prc受質的狀態改變造成的。根據先前的研究與我們實驗室的發現，有115個大腸桿菌蛋白有潛力可與Prc直接作用，表示它們有可能是Prc蛋白酶的受質。為了找出參與在prc基因缺失菌株移動能力的Prc受質，我們利用移動性測定法來進行篩選其中83個蛋白。在這些蛋白中，我們發現可能的Prc受質蛋白YceG和Pal，他們在細胞中的堆積降低了大腸桿菌的移動能力。然而，更進一步的實驗顯示YceG會被Prc蛋白酶降解而Pal並不會，表示只有YceG是Prc的受質。如同預期，prc基因缺失菌株中YceG的堆積是降低鞭毛蛋白FliC表現量的原因之一。這些結果表示，Prc受質YceG在prc基因缺失菌株中的堆積使FliC表現量下降，進而抑制大腸桿菌的移動能力。本研究增加對Prc蛋白酶參與在細菌移動能力機制的了解。

Pathogenic Escherichia coli cause many infectious diseases, such as neonatal meningitis, urinary tract infections and gastroenteritis. However, the rapid emerging antibiotic resistant strains have become a significant burden to treat such bacterial infections. Therefore, it is urgently needed to develop new antibiotic agents. The virulence factors of pathogenic bacteria are potential targets for developing novel antimicrobial strategies. The deficiency of the E. coli periplasmic protease Prc significantly decreases the bacterial motility. Given that bacterial motility contributes to the bacterial virulence, understanding the mechanism by which the protease affects the motility may facilitate the development of novel antimicrobial strategies. Because Prc is a protease, the decreased motility of the prc mutant is likely due to the alter fates of the Prc substrates in the mutant. Based on others and our previous studies, 115 E. coli proteins are shown to be possiblely to be able to interact with Prc directly, suggesting that they are potentail Prc substrates. We utilized motility assay to screen 83 of these proteins for Prc substrate that was responsible for the decreased motility of the prc mutant. Among these proteins, we found that the intracellular accumulation of the potential Prc substrate proteinsYceG and Pal decreased the bacterial motility. However, in the further investigation, we found that Prc protease degraded YceG but not Pal, suggesting that only YceG is a substrate of Prc. As expected, the accumulation of YceG in the prc mutant decreased the level of the flagellin FliC. Taken together, these results demonstrated that the accumulation of the Prc substrate YceG in the prc mutant decreases the expression of FliC, and thus to suppress the bacterial motility. This study facilitates our understanding how the Prc protease is involved in bacterial motiltity.

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