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The Replisome

The Replisome

DNA replication is carried out by a large complex of proteins that act in a coordinated matter to achieve high-fidelity DNA replication. Together this complex is known as the DNA replication machinery or the replisome.
The synthesis of the leading and lagging strands is a highly coordinated process. To explain this, the “Trombone model” was proposed by Bruce Alberts in 1980. The DNA loop formation starts when a primer is synthesized on the parent lagging strand. The loop grows with...

The Replisome

The Replisome

Bacterial Transformation

Bacterial Transformation

In 1928, bacteriologist Frederick Griffith worked on a vaccine for pneumonia, which is caused by Streptococcus pneumoniae bacteria. Griffith studied two pneumonia strains in mice: one pathogenic and one non-pathogenic. Only the pathogenic strain killed host mice.
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Bacterial Signaling

Bacterial Signaling

Bacterial signaling can occur within bacteria (intracellular) or between bacteria (intercellular). At times, a group of bacteria behaves like a community. To achieve this, they engage in quorum sensing, the perception of higher cell density that causes changes in gene expression. Quorum sensing involves both extracellular and intracellular signaling. The signaling cascade starts with a molecule called an autoinducer (AI). Individual bacteria produce AIs that move out of the bacterial cell...

Bacterial RNA Polymerase

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Unlike eukaryotes, bacteria use a single RNA Polymerase (RNAP) to transcribe all genes. The different subunits of bacterial RNAPhave distinct functions. The multisubunit structure of the bacterial RNAP helps the enzyme to maintain catalytic function, facilitate assembly, interact with DNA and RNA, and self-regulate its activity.
In most genes, the transcription site is a single base present upstream of the coding sequence. Though RNAP is a catalytically efficient enzyme, it does not recognize...

Bacterial Transcription

Bacterial Transcription

RNA polymerase (RNAP) carries out DNA-dependent RNA synthesis in both bacteria and eukaryotes. Bacteria do not have a membrane-bound nucleus. So, transcription and translation occur simultaneously, on the same DNA template.
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Related Experiment Video

Updated: Feb 4, 2026

Visualization of Replisome Encounters with an Antigen Tagged Blocking Lesion

Visualization of Replisome Encounters with an Antigen Tagged Blocking Lesion

Published on: July 27, 2021

Bacterial replisomes.

Zhi-Qiang Xu¹, Nicholas E Dixon¹

¹Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, and Illawarra Health and Medical Research Institute, Wollongong, New South Wales 2522, Australia.

Current Opinion in Structural Biology

|October 8, 2018

Summary

New structural and functional studies reveal bacterial DNA replication machines (replisomes) are less coordinated than previously thought. Polymerases and helicases may work independently, challenging the textbook model of a tightly coupled system.

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Last Updated: Feb 4, 2026

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Generation of Null Mutants to Elucidate the Role of Bacterial Glycosyltransferases in Bacterial Motility

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Published on: March 11, 2022

Area of Science:

Molecular Biology
Structural Biology
Biochemistry

Background:

Bacterial replisomes are complex protein machines responsible for DNA replication.
Understanding their structure and function is crucial for deciphering DNA replication mechanisms.
Previous models depicted replisomes as highly coordinated, integrated units.

Purpose of the Study:

To investigate the structural interactions within bacterial replisome subcomplexes.
To explore the functional dynamics and coordination of bacterial replisomes.
To challenge and refine the existing textbook model of DNA replication machinery.

Main Methods:

Single-particle cryo-electron microscopy (cryo-EM) to determine subcomplex structures.
Ensemble and single-molecule functional assays to study dynamics.
Fluorescence microscopy to visualize replisome components in action.

Main Results:

Detailed structures of Escherichia coli DNA polymerase III (core)-clamp-DNA subcomplexes were resolved in polymerization and proofreading states.
Evidence suggests bacterial replisomes operate stochastically, not as a rigidly coordinated machine.
Polymerases exhibit rapid exchange, and leading/lagging strand polymerases and helicase function more independently than expected.

Conclusions:

The intricate structural network of the polymerase-clamp subassembly provides insights into replisome mechanics.
Bacterial replisomes exhibit a decoupled and uncoordinated mode of operation.
These findings necessitate a revision of the traditional view of bacterial DNA replication machinery.