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Bacterio-opsin mutants of Halobacterium halobium
M Betlach1, F Pfeifer, J Friedman
1Howard Hughes Medical Institute and Department of Biochemistry and Biophysics, University of California, San Francisco, California 94143.
Summary
Cloning the bacterio-opsin (bop) gene revealed mutations in 11 of 12 Halobacterium halobium mutants, primarily upstream or within the gene. These inserts suggest polar effects on gene regulation or operon expression.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The bacterio-opsin (bop) gene in Halobacterium halobium R1 encodes a key protein for energy transduction.
- Understanding bop gene regulation is crucial for deciphering microbial energy metabolism.
Purpose of the Study:
- To clone and characterize the bacterio-opsin (bop) gene and its flanking regions in Halobacterium halobium R1.
- To analyze the genetic defects in bacterio-opsin mutants to understand gene regulation.
Main Methods:
- Cloning of the bop gene with approximately 40 kilobases of flanking genomic DNA.
- Subcloning of a 5.1-kilobase Pst I fragment containing the bop gene into pBR322.
- Restriction mapping and Southern blot analysis using defined fragments as probes to analyze 12 bop mutants.
Main Results:
- The 40-kilobase genomic segment is G+C-rich and not homologous to endogenous circular DNA.
- Eleven out of 12 bop mutants contained inserts (350-3,000 bp) within the bop gene or up to 1,400 bp upstream.
- Inserts were localized to four regions, including within the gene, overlapping its 5' end, and two upstream regions.
Conclusions:
- Mutational inserts likely cause polar effects, potentially inactivating regulatory genes or disrupting operon expression.
- The findings suggest that bop mRNA may be processed from a larger transcript, indicated by the 5' leader sequence.