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Related Concept Videos

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Proteins can form homomeric complexes with another unit of the same protein or heteromeric complexes with different types.  Most protein complexes self-assemble spontaneously via ordered pathways, while some proteins need assembly factors that guide their proper assembly. Despite the crowded intracellular environment, proteins usually interact with their correct partners and form functional complexes.
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Related Experiment Video

Updated: Jun 30, 2026

Hybrid Ensemble and Single-molecule Assay to Image the Motion of Fully Reconstituted CMG
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Hybrid Ensemble and Single-molecule Assay to Image the Motion of Fully Reconstituted CMG

Published on: July 26, 2024

Mcm subunits can assemble into two different active unwinding complexes.

Diane M Kanter1, Irina Bruck, Daniel L Kaplan

  • 1Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235, USA.

The Journal of Biological Chemistry
|September 20, 2008
PubMed
Summary
This summary is machine-generated.

The Mcm4-Mcm7 complex and Mcm4/Mcm6/Mcm7 assembly are active helicases that unwind DNA. These Mcm complexes show flexibility in subunit interactions, forming functional DNA unwinding motors.

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08:44

Generation and Purification of Human INO80 Chromatin Remodeling Complexes and Subcomplexes

Published on: October 23, 2014

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Genetics

Background:

  • Eukaryotic DNA replication fork helicase is a complex involving Mcm2-7, Cdc45, and GINS.
  • The Mcm2-7 complex is a heterohexameric ring responsible for ATP hydrolysis and motor function in DNA unwinding.
  • A detailed understanding of how individual Mcm subunit activities contribute to unwinding function is lacking.

Purpose of the Study:

  • To investigate the mechanism of the Mcm4-Mcm6-Mcm7 complex as a model system for helicase activity.
  • To examine the biochemical properties of different Mcm subunit combinations.
  • To understand the relationship between Mcm subunit interactions, ATPase activity, and DNA unwinding.

Main Methods:

  • Purification of individual Mcm subunits (Mcm4, Mcm6, Mcm7) to nuclease-free status.
  • Biochemical analysis of various Mcm subunit combinations.
  • Assays for helicase activity, ATPase activity, and DNA binding/unwinding.
  • Electron microscopy to assess complex formation (ring structure).

Main Results:

  • Mcm4 and Mcm7 form an active DNA unwinding assembly.
  • Mcm6 addition to Mcm4/Mcm7 creates an active Mcm4/Mcm6/Mcm7 helicase.
  • Both Mcm4-Mcm7 and Mcm4/Mcm6/Mcm7 complexes form ring-shaped hexamers with 3' to 5' polarity.
  • These complexes exhibit DNA-stimulated ATPase activity and can open to load onto circular DNA.

Conclusions:

  • Mcm subunits display significant flexibility and dynamic interactions in forming active DNA unwinding complexes.
  • The Mcm4-Mcm7 and Mcm4/Mcm6/Mcm7 assemblies are functional helicases with distinct biochemical properties.
  • The ability to form rings and stimulate ATPase activity correlates with DNA unwinding capability.