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Related Experiment Videos

Dihydrofolate reductase gene as a versatile expression marker.

M Iwakura1, T Tanaka

  • 1Research Institute for Polymers and Textiles, Ibaraki.

Journal of Biochemistry
|January 1, 1992
PubMed
Summary

Researchers developed versatile plasmids using the Escherichia coli dihydrofolate reductase (DHFR) gene for trimethoprim resistance (TmpR) selection. These tools enable efficient evaluation of gene expression elements and protein production.

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Area of Science:

  • Molecular Biology
  • Biotechnology
  • Microbial Genetics

Background:

  • The Escherichia coli dihydrofolate reductase (DHFR) gene is recognized for conferring trimethoprim resistance (TmpR).
  • Existing methods for genetic marker selection can be cumbersome.
  • A need exists for versatile expression markers in molecular biology.

Purpose of the Study:

  • To construct versatile plasmid systems utilizing the DHFR gene as an expression marker.
  • To facilitate the selection of recombinant plasmids via trimethoprim resistance.
  • To enable the evaluation of promoter and terminator efficiencies in fused DNA fragments.

Main Methods:

  • Construction of three plasmid types: promoter cloning vector, terminator cloning vector, and a DHFR gene cassette plasmid.
  • Selection of recombinant plasmids based on the trimethoprim resistance (TmpR) phenotype in transformed cells.
  • Measurement of DHFR enzymatic activity to assess promoter and terminator function.
  • Modification of promoter and Shine-Dalgarno sequences to optimize DHFR expression.

Main Results:

  • Successfully constructed versatile plasmid systems for gene expression studies.
  • Trimethoprim resistance (TmpR) phenotype provided a straightforward selection method.
  • DHFR enzymatic activity measurements effectively evaluated promoter and terminator efficiencies.
  • An expression plasmid was created enabling DHFR production up to 20% of total cellular proteins in E. coli.

Conclusions:

  • The developed DHFR-based plasmid systems offer a versatile and efficient tool for molecular cloning and gene expression analysis.
  • The TmpR phenotype serves as a reliable marker for recombinant plasmid selection.
  • Optimized expression constructs can lead to high levels of protein production in E. coli.

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