期刊
NATURE CHEMICAL BIOLOGY
卷 11, 期 8, 页码 579-U75出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/NCHEMBIO.1857
关键词
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资金
- Australian Research Council [DP0877658]
- Netherlands Organisation for Scientific Research (NWO)
- European Research Council
- Australian Research Council [DP0877658] Funding Source: Australian Research Council
The bidirectional replication of a circular chromosome by many bacteria necessitates proper termination to avoid the head-on collision of the opposing replisomes. In Escherichia coli, replisome progression beyond the termination site is prevented by Tus proteins bound to asymmetric Ter sites. Structural evidence indicates that strand separation on the blocking (nonpermissive) side of Tus-Ter triggers roadblock formation, but biochemical evidence also suggests roles for protein-protein interactions. Here DNA unzipping experiments demonstrate that nonpermissively oriented Tus-Ter forms a tight lock in the absence of replicative proteins, whereas permissively oriented Tus-Ter allows nearly unhindered strand separation. Quantifying the lock strength reveals the existence of several intermediate lock states that are impacted by mutations in the lock domain but not by mutations in the DNA-binding domain. Lock formation is highly specific and exceeds reported in vivo efficiencies. We postulate that protein-protein interactions may actually hinder, rather than promote, proper lock formation.
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