A robust genetic system for producing heterodimeric native and mutant cytochrome bc(1).

Area of Science:

• Biochemistry
• Molecular Biology
• Bioenergetics

Background:

• Cytochrome bc1 (ubiquinone:cytochrome c oxidoreductase) is crucial for ATP production via oxidative and photophosphorylation.
• Previous genetic studies of heterodimeric cytochrome bc1 variants faced challenges due to genetic rearrangements in plasmid systems with gene duplications.
• Homologous recombination in these systems can lead to heterogeneous populations, complicating mechanistic studies.

Purpose of the Study:

• To investigate the origins and frequencies of genetic variations in existing two-plasmid systems for cytochrome bc1 variant production.
• To develop and describe an improved two-plasmid system that minimizes genetic instability.
• To enable reliable production of native and mutant heterodimeric cytochrome bc1 variants for bioenergetic studies.

Main Methods:

• Assessed genetic variation origins and frequencies in one- and two-plasmid systems.
• Engineered a recombination-deficient (recA) bacterial background.
• Utilized a modified two-plasmid system in the recA background to produce heterodimeric cytochrome bc1 variants.

Main Results:

• The recombination-deficient (recA) background significantly minimized spontaneous co-integrant plasmid formation.
• Homologous recombination within cytochrome b gene copies became inconsequential in the recA system.
• Both the improved RecA-deficient and the original RecA-proficient two-plasmid systems reliably produced heterodimeric cytochrome bc1 variants.

Conclusions:

• The improved two-plasmid system in a recA background reliably produces native and mutant heterodimeric cytochrome bc1 variants.
• This system minimizes genetic variations, offering a more stable platform for studying enzyme mechanisms.
• The developed system can aid in creating and studying "mitochondrial heteroplasmy"-like states in model bacteria for bioenergetics research.