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Published on: September 10, 2015
Translational coupling controls expression and function of the DrrAB drug efflux pump
Prajakta Pradhan1, Wen Li, Parjit Kaur
1Department of Biology, Georgia State University, Atlanta, GA 30303, USA.
Journal of Molecular Biology
|December 10, 2008
Summary
Translational coupling of drrA and drrB genes is essential for producing a functional doxorubicin efflux pump in Streptomyces peucetius. This coupling ensures proper protein assembly and regulates expression, preventing growth inhibition.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- DrrA and DrrB proteins form an efflux pump exporting anticancer drugs doxorubicin and daunorubicin in Streptomyces peucetius.
- Previous observations indicated DrrA and DrrB confer doxorubicin resistance only when co-expressed (in cis).
- Overlapping codons suggested translational coupling between drrA and drrB, but direct evidence was lacking.
Purpose of the Study:
- To investigate the role of translational coupling in the expression and function of DrrA and DrrB proteins.
- To provide direct evidence for translational coupling between drrA and drrB.
- To elucidate the impact of translational coupling on the assembly and function of the DrrAB efflux pump.
Main Methods:
- Genetic manipulation to introduce non-coding sequences between drrA and drrB.
- Gene replacement experiments to substitute drrA with an unrelated gene.
- Analysis of protein production levels and functional complex formation.
Main Results:
- Direct evidence confirmed that drrB expression is translationally coupled to drrA.
- Interruption of coupling by non-coding sequences prevented functional complex formation, despite normal protein production.
- Replacing drrA led to excessive drrB expression and severe growth inhibition.
Conclusions:
- Translational coupling is crucial for the proper assembly of the DrrAB efflux pump.
- Co-folding of DrrA and DrrB, facilitated by translational coupling, is key to complex formation.
- DrrA contains a mechanism to optimize drrB expression, preventing toxicity.
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