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Related Experiment Videos

Electrostatic forces contribute to interactions between trp repressor dimers

K S Martin1, C A Royer, K P Howard

  • 1School of Pharmacy, University of Wisconsin-Madison 53706.

Biophysical Journal
|April 1, 1994
PubMed
Summary
This summary is machine-generated.

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The trp repressor (TR) from Escherichia coli forms higher-order aggregates in solution, challenging the view of it being solely dimeric. Corepressor binding destabilizes these aggregates, suggesting a role in TR’s regulatory function.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Protein Dynamics

Background:

  • The trp repressor (TR) from Escherichia coli is traditionally considered a dimer.
  • Previous studies suggested TR oligomerization at micromolar concentrations.
  • The intrinsic nature of this oligomerization required further investigation.

Purpose of the Study:

  • To provide definitive evidence for the oligomerization of unmodified TR dimers into higher-order aggregates.
  • To investigate the influence of corepressor binding on TR aggregation.
  • To elucidate the factors, such as salt and pH, affecting TR oligomerization.

Main Methods:

  • Chemical cross-linking to detect aggregate formation.
  • Analytical ultracentrifugation to determine molecular weight and aggregation states.

Related Experiment Videos

  • Molecular sieve chromatography (gel filtration) to assess aggregate size distribution.
  • Investigation of salt and pH dependence to understand interaction forces.

    • Main Results:

    • Chemical cross-linking confirmed the formation of tetramers and higher-order species at concentrations between 1 and 40 microM.
    • Analytical ultracentrifugation and gel filtration indicated average molecular weights between dimer and tetramer, with evidence of populated higher-order species.
    • Corepressor binding was shown to destabilize these higher-order aggregates.
    • Oligomerization exhibited dependence on salt concentration and pH, revealing an electrostatic component.

    Conclusions:

    • TR dimers intrinsically form higher-order aggregates in solution.
    • Corepressor binding likely modulates TR activity by destabilizing these aggregates.
    • Electrostatic interactions play a significant role in the oligomerization of TR dimers.