Nucleotide- and stoichiometry-dependent DNA supercoiling by reverse gyrase

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• Reverse gyrase is a unique Type IA topoisomerase capable of introducing positive supercoils into DNA.
• Understanding its biochemical properties is crucial for elucidating DNA topology regulation in archaea.

Purpose of the Study:

• To investigate the biochemical properties of Archaeoglobus fulgidus reverse gyrase.
• To determine the influence of adenine nucleotide cofactors and enzyme stoichiometry on supercoiling activity.
• To explore the effect of temperature on reverse gyrase function.

Main Methods:

• In vitro supercoiling assays using Archaeoglobus fulgidus reverse gyrase.
• Analysis of DNA topological changes mediated by different adenine nucleotide cofactors (ATP, AMPPNP, ADP).
• Investigation of enzyme-to-DNA stoichiometry and temperature effects on reaction outcomes.

Main Results:

• Reverse gyrase mediates three distinct supercoiling reactions (positive, negative, relaxation) dependent on the adenine nucleotide cofactor.
• The final supercoiling extent is determined by enzyme-to-DNA stoichiometry, not reaction rate.
• Enzyme activity dramatically increases between 80°C and 85°C, correlating with DNA pre-melting and extensive unwinding.

Conclusions:

• Archaeoglobus fulgidus reverse gyrase exhibits cofactor-dependent modulation of DNA supercoiling.
• Enzyme stoichiometry is a critical determinant of the final DNA topological state.
• Elevated temperatures within the organism's optimal range significantly enhance reverse gyrase activity, potentially by inducing DNA unwinding.