Mutations simultaneously affecting endonuclease II and exonuclease III in Escherichia coli.
AUTOR(ES)
Yajko, D M
RESUMO
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 methyl-methanesulfonate and mitomycin C, and a decreased plating efficiency for bacteriophage lambda, but no marked sensitivity to ultraviolet or gamma-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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=432380Documentos Relacionados
- Preliminary Mapping of Mutations Affecting Exonuclease III in Escherichia coli K-12
- Endonuclease II, apurinic acid endonuclease, and exonuclease III.
- Endonuclease III (nth) mutants of Escherichia coli.
- Exonuclease III and endonuclease IV remove 3' blocks from DNA synthesis primers in H2O2-damaged Escherichia coli.
- Plasmid mutations affecting self-maintenance and host growth in Escherichia coli.