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Related Concept Videos

The DNA Replication Fork01:02

The DNA Replication Fork

An organism’s genome needs to be duplicated in an efficient and error-free manner for its growth and survival. The replication fork is a Y-shaped active region where two strands of DNA are separated and replicated continuously. The coupling of DNA unzipping and complementary strand synthesis is a characteristic feature of a replication fork.   Organisms with small circular DNA, such as E. coli, often have a single origin of replication; therefore, they have only two replication forks, one in...
DNA Helicases00:55

DNA Helicases

DNA unwinding helicase enzymes are a type of motor protein. Motor proteins can translocate along filaments or polymers using energy generated from ATP hydrolysis. Helicases are involved in all the important cellular processes where DNA unwinding is required, such as DNA replication, repair, recombination, and transcription. They are present in all living organisms, but vary in their structure, function, and mechanism of action. For example, in prokaryotes, DnaB helicase binds and translocates...
The Replisome03:01

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...
DNA Topoisomerases02:02

DNA Topoisomerases

Topoisomerases are enzymes that relax overwound DNA molecules during various cell processes, including DNA replication and transcription. These enzymes regulate positive and negative DNA supercoiling without changing the nucleotide sequence. DNA overwinding in a clockwise direction results in positively supercoiled DNA, whereas underwinding in a counterclockwise direction produces negatively supercoiled DNA.
Types and Mechanism of action
Topoisomerases are divided into two main types.  Type I...
Restarting Stalled Replication Forks02:37

Restarting Stalled Replication Forks

DNA replication is initiated at sites containing predefined DNA sequences known as origins of replication. DNA is unwound at these sites by the minichromosome maintenance (MCM) helicase and other factors such as Cdc45 and the associated GINS complex.The unwound single strands are protected by replication protein A (RPA) until DNA polymerase starts synthesizing DNA at the 5’ end of the strand in the same direction as the replication fork. To prevent the replication fork from falling apart, a...
The DNA Replication Fork01:02

The DNA Replication Fork

An organism’s genome needs to be duplicated in an efficient and error-free manner for its growth and survival. The replication fork is a Y-shaped active region where two strands of DNA are separated and replicated continuously. The coupling of DNA unzipping and complementary strand synthesis is a characteristic feature of a replication fork.   Organisms with small circular DNA, such as E. coli, often have a single origin of replication; therefore, they have only two replication forks, one in...

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Updated: May 7, 2026

Single-molecule Manipulation of G-quadruplexes by Magnetic Tweezers
08:28

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Published on: September 19, 2017

A helicase with an extra spring in its step.

Michael Schlierf1, Taekjip Ha

  • 1B CUBE, Center for Molecular Bioengineering, Technische Universität Dresden, 01062 Dresden, Germany. schlierf@bcube-dresden.de

Cell
|October 16, 2012
PubMed
Summary
This summary is machine-generated.

DNA helicases are essential for replication. A new study reveals how the DnaB helicase unwinds DNA two base pairs at a time using a unique mechanism.

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Area of Science:

  • Molecular Biology
  • Biochemistry
  • Structural Biology

Background:

  • DNA replication relies on hexameric ring-shaped helicases to unwind double-stranded DNA.
  • Understanding the precise mechanism of DNA unwinding is crucial for comprehending DNA replication fidelity and regulation.

Discussion:

  • Itsathitphaisarn et al. present a high-resolution crystal structure of the DnaB helicase.
  • The structure captures DnaB in complex with single-stranded DNA and nucleotide triphosphate analogs.
  • This complex reveals a novel mechanism for DNA unwinding.

Key Insights:

  • The DnaB helicase employs a unique mechanism to unwind DNA.
  • The unwinding process occurs at a rate of two base pairs at a time.
  • Structural data provides unprecedented insight into helicase function.

Outlook:

  • Further structural and biochemical studies will elucidate the dynamics of DnaB during DNA unwinding.
  • This research may inform the development of novel therapeutic strategies targeting DNA replication.
  • Understanding DnaB's mechanism could have implications for antiviral or anticancer drug design.