芳香化合物廣泛存在于自然界，其代謝循環(huán)是地球化學(xué)元素循環(huán)的重要組成部分,；同時(shí),，作為現(xiàn)代工業(yè)的重要原材料，芳香化合物在使用過程中大量排放到環(huán)境中,，給生態(tài)系統(tǒng)帶來了巨大壓力,。微生物經(jīng)過適應(yīng)和進(jìn)化，形成了多種豐富的芳香化合物代謝途徑,，這些代謝途徑的調(diào)控機(jī)制,，是環(huán)境微生物學(xué)關(guān)注的研究熱點(diǎn)。
谷氨酸棒桿菌是一株革蘭氏陽性的土壤細(xì)菌,，長期以來作為重要的氨基酸生產(chǎn)菌在工業(yè)上廣泛應(yīng)用,。中科院微生物研究所微生物資源前期開發(fā)國家重點(diǎn)實(shí)驗(yàn)室環(huán)境微生物技術(shù)中心劉雙江課題組以該菌種為模式菌，對多條完整的芳香化合物代謝途徑進(jìn)行了系統(tǒng)研究和報(bào)道,。在前期研究的基礎(chǔ)上,，研究組進(jìn)一步研究了芳香化合物代謝的調(diào)控,，近期先后報(bào)道了原兒茶酸代謝途徑調(diào)控蛋白（PcaO）、苯乙酸代謝途徑調(diào)控蛋白（PaaR）,、間苯二酚代謝調(diào)控蛋白（RolR）等的作用機(jī)制,。
研究間苯二酚代謝的調(diào)控機(jī)制發(fā)現(xiàn)，間苯二酚代謝基因簇上的一個(gè)TetR類調(diào)控蛋白RolR,，通過結(jié)合到一個(gè)29-bp的操縱基因rolO上,，同時(shí)負(fù)調(diào)控其自身基因及該基因簇上反向轉(zhuǎn)錄的結(jié)構(gòu)基因的轉(zhuǎn)錄，而間苯二酚及其中間代謝產(chǎn)物偏苯三酚可以解除RolR的抑制作用,，推測RolR可能通過roadblock機(jī)制來抑制其靶基因的轉(zhuǎn)錄,，這是首次報(bào)導(dǎo)TetR類調(diào)控蛋白采用roadblock機(jī)制負(fù)調(diào)控靶基因的轉(zhuǎn)錄。晶體結(jié)構(gòu)解析發(fā)現(xiàn),，當(dāng)RolR與效應(yīng)物結(jié)合形成復(fù)合體后,，RolR兩個(gè)亞基的DNA結(jié)合域中心距離從34.9Å縮小到30.4Å，使得復(fù)合物不能與DNA靶點(diǎn)結(jié)合,，消除了轉(zhuǎn)錄抑制,，轉(zhuǎn)錄得以進(jìn)行。
此外,，研究組與德國比勒菲爾德大學(xué)合作,，鑒定了谷氨酸棒桿菌AS 1.542中的苯乙酸（PAA）代謝基因簇和一個(gè)TetR類調(diào)控蛋白（PaaR）。PaaR通過結(jié)合到長度為22 bp的非完美回文序列上,，負(fù)調(diào)控PAA代謝基因的轉(zhuǎn)錄,，而PAA的代謝產(chǎn)物苯乙酰輔酶A可以解除PaaR的抑制作用；研究還發(fā)現(xiàn),，谷氨酸棒桿菌中的全局調(diào)控因子GlxR也可以結(jié)合到PAA代謝基因簇的上游,，暗示GlxR也參與了PAA代謝基因簇轉(zhuǎn)錄的調(diào)控。生物信息學(xué)分析發(fā)現(xiàn),，在Actinobacteria、Proteobacteria和Flavobacteria等57個(gè)細(xì)菌基因組中都存在相似的PaaR調(diào)節(jié)單元,，暗示類似PaaR的調(diào)控機(jī)制可能廣泛存在于這些細(xì)菌中,。
這些研究進(jìn)展有利于深入認(rèn)識微生物代謝芳香化合物過程中的調(diào)控機(jī)制，已于近期發(fā)表于Appl. Environ. Microbiol雜志上,。相關(guān)研究得到了國家自然科學(xué)基金和國家科技部973計(jì)劃的支持,。（生物谷Bioon.com）
doi:10.1128/AEM.01304-12
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The TetR-type transcriptional repressor RolR from Corynebacterium glutamicum regulates resorcinol catabolism by binding to a unique operator rolO
Tang Li1,2, Kexin Zhao1, Yan Huang1, Defeng Li3, Cheng-Ying Jiang1,2, Nan Zhou1,2, Zheng Fan4 and Shuang-Jiang Liu1,2,*
The rol (designated for resorcinol) gene cluster rolRHMD is involved in resorcinol catabolism in Corynebacterium glutamicum, and RolR is the TetR-type regulator. In this study, we investigated how RolR regulated the transcription of the rol genes in C. glutamicum. The transcription start sites and promoters of rolR and rolHMD were identified. RT-qPCR and promoter activity analysis indicated that RolR negatively regulated the transcription of rolHMD and of its own gene. Further, a 29-bp operator rolO was located at the intergenic region of rolR and rolHMD and was identified as the sole binding site for RolR. It contained two overlapping inverted repeats and they were essential for RolR-binding. The binding of RolR to rolO was affected by resorcinol and hydroxyquinol, which are the starting compounds of resorcinol catabolic pathway. These two compounds were able to dissociate RolR-rolO complex, thus releasing RolR from the complex and derepressing the transcription of rol genes in C. glutamicum. It is proposed that the binding of RolR to its operator rolO blocks the transcription of rolHMD and of its own gene, thus negatively regulated resorcinol degradation in C. glutamicum.
