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Related Concept Videos

Homologous Recombination02:31

Homologous Recombination

The basic reaction of homologous recombination (HR) involves two chromatids that contain DNA sequences sharing a significant stretch of identity. One of these sequences uses a strand from another as a template to synthesize DNA in an enzyme-catalyzed reaction. The final product is a novel amalgamation of the two substrates. To ensure an accurate recombination of sequences, HR is restricted to the S and G2 phases of the cell cycle. At these stages, the DNA has been replicated already and the...
Nucleosome Remodeling02:54

Nucleosome Remodeling

Nucleosomes are the basic units of chromatin compaction. Each nucleosome consists of the DNA bound tightly around a histone core, which makes the DNA inaccessible to DNA binding proteins such as DNA polymerase and RNA polymerase. Hence, the fundamental problem is to ensure access to DNA when appropriate, despite the compact and protective chromatin structure.
Nucleosome remodeling complex
Eukaryotic cells have specialized enzymes called ATP-dependent nucleosome remodeling enzymes. These enzymes...
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...
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...
Conservative Site-specific Recombination and Phase Variation02:53

Conservative Site-specific Recombination and Phase Variation

Because the DNA segments are cut and reorganized in a direction-specific manner, site-specific recombination has emerged as an efficient genetic engineering technique. Flippase and Cyclization recombinases or Flp and Cre, respectively, are two members of the tyrosine recombinase family derived from bacteriophages, that are used to mediate site-specific DNA insertions, deletions, and targeted expression of proteins in mammalian cell lines.
The recognition sites for Cre recombinase called LoxP...

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Related Experiment Video

Updated: Jun 7, 2026

A G-quadruplex DNA-affinity Approach for Purification of Enzymatically Active G4 Resolvase1
11:25

A G-quadruplex DNA-affinity Approach for Purification of Enzymatically Active G4 Resolvase1

Published on: March 18, 2017

RNA remodeling by hexameric RNA helicases.

Makhlouf Rabhi1, Roman Tuma, Marc Boudvillain

  • 1CNRS UPR4301, Centre de Biophysique Moléculaire, Orléans cedex, France.

RNA Biology
|November 4, 2010
PubMed
Summary

RNA helicases unwind RNA and disrupt RNA-protein complexes. This review compares the structures and mechanisms of the bacteriophage φ8 P4 motor and E. coli Rho factor, highlighting similarities and differences in their homo-hexameric ring functions.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Structural Biology

Background:

  • RNA helicases are essential NTP-dependent enzymes involved in cellular metabolism.
  • They are responsible for unwinding RNA and disrupting RNA-protein complexes.
  • Many RNA helicases share a homo-hexameric ring structure.

Purpose of the Study:

  • To review the structures, mechanisms, and biochemical properties of two specific RNA helicases.
  • To compare and contrast the mechanisms of the bacteriophage φ8 P4 packaging motor and Escherichia coli Rho transcription termination factor.
  • To identify similarities and differences between these two homo-hexameric ring helicases.

Main Methods:

  • Structural analysis of RNA helicases.
  • Mechanistic studies of enzyme function.

Related Experiment Videos

Last Updated: Jun 7, 2026

A G-quadruplex DNA-affinity Approach for Purification of Enzymatically Active G4 Resolvase1
11:25

A G-quadruplex DNA-affinity Approach for Purification of Enzymatically Active G4 Resolvase1

Published on: March 18, 2017

  • Biochemical characterization of enzymatic properties.

    • Main Results:

    • The P4 motor (Super-Family 4) and Rho factor (Super-Family 5) both adopt homo-hexameric ring architectures.
    • Detailed comparison of their structures and biochemical properties.
    • Identification of key mechanistic similarities and differences between Rho and P4.

    Conclusions:

    • Despite distinct biological roles, Rho and P4 helicases share conserved features due to their homo-hexameric ring structure.
    • Understanding these shared and divergent mechanisms provides insights into RNA helicase function.
    • Further research is needed to fully elucidate the remaining questions regarding their mechanisms.