Reverse gyrase has heat-protective DNA chaperone activity independent of supercoiling
Reverse gyrase has heat-protective DNA chaperone activity independent of supercoiling
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DOI：
10.1093/nar/gkh683
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发表时间：
2004-07-01
影响因子：
14.9
通讯作者：
Stock, D
中科院分区：
文献类型：
--
作者：
Kampmann, M;Stock, D
极端嗜热生物必须保护其组成大分子免受热诱导降解。活性细胞中DNA热保护的一般机制尚不清楚。我们发现，反向旋转酶，唯一的蛋白质，这是特异性和共同的所有超嗜热菌，减少双链DNA断裂的速度在90摄氏度约8倍。这种活性不需要ATIP水解，并且不依赖于酶的正超螺旋活性。反向旋转酶对脱嘌呤速率有轻微的非特异性影响，对双链断裂速率有主要的特异性影响。使用电子显微镜，我们发现，反向旋转酶识别切口的DNA和招聘的蛋白质外壳的损伤部位通过合作结合。类似于分子伴侣，协助未折叠的蛋白质，我们发现，反向旋转酶防止不适当的聚集变性DNA区域，并促进正确的退火。我们提出了一个有针对性的保护机制，在体内的反向旋转酶检测受损的DNA，并作为分子夹板，以防止在病变附近的DNA断裂，从而保持受损的DNA的构象，是适合修复的模型。
Hyperthermophilic organisms must protect their constituent macromolecules from heat-induced degradation. A general mechanism for thermoprotection of DNA in active cells is unknown. We show that reverse gyrase, the only protein that is both specific and common to all hyperthermophiles, reduces the rate of double-stranded DNA breakage similar to8-fold at 90degreesC. This activity does not require ATIP hydrolysis and is independent of the positive supercoiling activity of the enzyme. Reverse gyrase has a minor nonspecific effect on the rate of depurination, and a major specific effect on the rate of double-strand breakage. Using electron microscopy, we show that reverse gyrase recognizes nicked DNA and recruits a protein coat to the site of damage through cooperative binding. Analogously to molecular chaperones that assist unfolded proteins, we found that reverse gyrase prevents inappropriate aggregation of denatured DNA regions and promotes correct annealing. We propose a model for a targeted protection mechanism in vivo in which reverse gyrase detects damaged DNA and acts as a molecular splint to prevent DNA breakage in the vicinity of the lesion, thus maintaining damaged DNA in a conformation that is amenable to repair.