Mutations Simultaneously Affecting Endonuclease II and Exonuclease III in Escherichia coli

We studied mutants of E. coli originally identified as being deficient in either endonuclease II (deoxyribonucleate oligonucleotidohydrolase, EC 3.1.4.30) or exonuclease III [deoxyribonucleate (double-stranded) 5′-nucleotidohydrolase, EC 3.1.4.27] activity. Twelve independently derived mutants were...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1975-02, Vol.72 (2), p.688-692
Main Authors: Yajko, David M., Weiss, Bernard
Format: Article
Language:English
Subjects:
Bacteriophages
Broths
Cell growth
Chromosome Mapping
Coliphages
Deoxyribonucleases - biosynthesis
DNA
Endonucleases - biosynthesis
Enzyme activity
Enzymes
Escherichia coli - enzymology
Exonucleases - biosynthesis
Gels
Genes
Genetic Linkage
Genetic mutation
Mutation
Phenotype
Sprains and strains
Temperature
Transduction, Genetic
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Summary:We studied mutants of E. coli originally identified as being deficient in either endonuclease II (deoxyribonucleate oligonucleotidohydrolase, EC 3.1.4.30) or exonuclease III [deoxyribonucleate (double-stranded) 5′-nucleotidohydrolase, EC 3.1.4.27] activity. Twelve independently derived mutants were tested, including three new endonuclease II mutants. Deficiency of one enzyme was always accompanied by deficiency of the other. Furthermore, temperature-sensitivity of one activity was always accompanied by temperature-sensitivity of the other, and the enzymes were co-purified. The results suggested a physical association between exonuclease III and endonuclease II, which may be of advantage in the excision-repair of DNA. A thermolabile endonuclease II was purified from one of the new mutants, indicating that it had an altered structural gene. This mutation, and all similar ones mapped by genetic transduction, was located between the pncA and aroD genes on the E. coli chromosome. One mutant had a prolonged generation time, an increased sensitivity to the alkylating agents methylmethanesulfonate and mitomycin C, and a decreased plating efficiency for bacteriophage λ , but no marked sensitivity to ultraviolet or γ -irradiation. Its enzymatic and biological abnormalities were simultaneously revertible, suggesting they were caused by a single mutation. These results suggested a role for these enzymes in normal cell growth processes and in the repair of alkylation damage.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.72.2.688