The pepN gene, that encodes aminopeptidase N in Escherichia coli, has been cloned into the multicopy plasmid pBR322. Expression of the cloned pepN gene results in overproduction of the enzyme. The restriction map of the 6.7 Kb insert was established and the gene was further localized by analysis of
Cloning of Escherichia coli genes encoding 3-methyladenine DNA glycosylases I and II
β Scribed by Clarke, Neil D. ;Kvaal, Marit ;Seeberg, Erling
- Publisher
- Springer
- Year
- 1984
- Tongue
- English
- Weight
- 507 KB
- Volume
- 197
- Category
- Article
- ISSN
- 0026-8925
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β¦ Synopsis
We have constructed two recombinant plasmids which harbour functions involved in DNA repair of alkylation damage in Escherichia coli. One plasmid carries the tag+ gene encoding 3-methyladenine DNA glycosylase I while the other carries alkA+ encoding 3-methyladenine DNA glycosylase II. The plasmids were isolated from plasmid stocks carrying total cellular DNA by selection for their ability to complement the methylmethanesulphonate(MMS)-sensitive phenotype of an E. coli mutant (tag ada) deficient in both 3-methyladenine DNA glycosylases I and II. Both plasmids increase the plating efficiency of such a mutant on methylmethanesulphonate plates by a factor of more than 10(5). The tag gene is located on a 6 (kbp) HindIII fragment, and the presence of the tag plasmid in the cells results in 15-fold overproduction of 3-methyladenine DNA glycosylase I. The other plasmid restores 3-methyladenine DNA glycosylase II deficiency in alkA mutant cells, and results in 3-fold overproduction of this enzyme after alkylation induction. The induction is ada+-dependent and we conclude that this plasmid contains the structural gene for 3-methyladenine DNA glycosylase II, including its control region responding to alkylation induction. However, the plasmid does not complement fully the MMS-sensitive phenotype of alkA mutants which suggests that the plasmid may not include the entire alkA operon.
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