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Two mechanisms coordinate replication termination by the Escherichia coli Tus-Ter complex

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posted on 2024-11-16, 07:18 authored by Manjula Pandey, Mohamed M Elshenawy, Slobodan Jergic, Masateru Takahashi, Nicholas DixonNicholas Dixon, Samir M Hamdan, Smita S Patel
The Escherichia coli replication terminator protein (Tus) binds to Ter sequences to block replication forks approaching from one direction. Here, we used single molecule and transient state kinetics to study responses of the heterologous phage T7 replisome to the Tus-Ter complex. The T7 replisome was arrested at the non-permissive end of Tus-Ter in a manner that is explained by a composite mousetrap and dynamic clamp model. An unpaired C(6) that forms a lock by binding into the cytosine binding pocket of Tus was most effective in arresting the replisome and mutation of C(6) removed the barrier. Isolated helicase was also blocked at the non-permissive end, but unexpectedly the isolated polymerase was not, unless C(6) was unpaired. Instead, the polymerase was blocked at the permissive end. This indicates that the Tus-Ter mechanism is sensitive to the translocation polarity of the DNA motor. The polymerase tracking along the template strand traps the C(6) to prevent lock formation; the helicase tracking along the other strand traps the complementary G(6) to aid lock formation. Our results are consistent with the model where strand separation by the helicase unpairs the GC(6) base pair and triggers lock formation immediately before the polymerase can sequester the C(6) base.

Funding

Functional Dissection of the Bacterial Replisome

Australian Research Council

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History

Citation

Pandey, M., Elshenawy, M. M., Jergic, S., Takahashi, M., Dixon, N. E., Hamdan, S. M. & Patel, S. S. (2015). Two mechanisms coordinate replication termination by the Escherichia coli Tus-Ter complex. Nucleic Acids Research, 43 (12), 5924-5935.

Journal title

Nucleic Acids Research

Volume

43

Issue

12

Pagination

5924-5935

Language

English

RIS ID

102806

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