RECOMBINATION OF NICKED DNA KNOTS BY GAMMA-DELTA RESOLVASE SUGGESTS A VARIANT MODEL FOR THE MECHANISM OF STRAND EXCHANGE

被引:6
作者
DROGE, P
机构
[1] Department of Biology, University of Konstanz, D-7750 Konstanz
关键词
D O I
10.1093/nar/20.23.6159
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Fast and efficient recombination catalyzed by gammadelta resolvase in vitro requires negative DNA supercoiling of plasmid substrates. The current model for recombination suggests that supercoiling is required to drive DNA strand exchange within a synaptic complex by 'simple rotation' of DNA-linked resolvase protomers. Surprisingly, DNA knots are recombined efficiently in the absence of supercoiling, whereby the rate of recombination increases with the number of irreducible DNA segment crossings, or nodes, within each substrate knot. Recombination products contain three knot nodes less than substrates, suggesting that a reduction in writhe drives the reaction. However, the proposed protomer rotation model predicts that writhe is not altered during the process of strand transfer but, instead, is reduced only when a synaptic complex disassembles after strand exchange. I present evidence that recombination of knotted and of linear substrates coincides with a disassembly of synaptic complexes. The results lead to a variant model for strand exchange on non-supercoiled substrates in which a specific disassembly of the synaptic complex, triggered by a reduction in writhe, guides the cleaved DNA into the recombinant configuration.
引用
收藏
页码:6159 / 6166
页数:8
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