Physical and biochemical characterization of cloned sbcB and xonA mutations from Escherichia coli K-12

Journal Article · Sun May 01 00:00:00 EDT 1988 · J. Bacteriol.; (United States)

OSTI ID:7152343

Phillips, G J; Prasher, D C; Kushner, S R

In Escherichia coli K-12, sbcB/xonA is the structural gene for exonuclease I, an enzyme that hydrolyzes single-stranded DNA to mononucleotides in the 3'-to-5' direction. This enzyme has been implicated in the DNA repair and recombination pathways mediated by the recB and recC gene products (exonuclease V). We have cloned several sbcB/xonA mutant alleles in bacterial plasmids and have partially characterized the cloned genes and their protein products. Two of the mutations (xonA2 and xonA6) retain no detectable exonucleolytic activity on single-stranded DNA. The xonA6 allele was shown to harbor an insertion of an IS30-related genetic element near the 3' end of the gene. Two other mutations, sbcB15 and xonA8, exhibited significantly reduced levels of exonuclease I activity as compared to the cloned wild-type gene. A correlation was observed between levels of exonuclease I activity and the ability of the sbcB/xonA mutations to suppress UV sensitivity in recB and recC strains. Also, recombinant plasmids bearing either the sbcB15 or xonA6 allele exhibited a high degree of instability during growth of their bacterial hosts. The results suggest that the sbcB/xonA gene product is a bi- or multifunctional protein that interacts with single-stranded DNA and possibly with other proteins in the suppression of genetic recombination and DNA-repair deficiencies in recB and recC mutants.

• Research Organization: Univ. of Georgia, Athens (USA)
• OSTI ID: 7152343
• Journal Information: J. Bacteriol.; (United States), Vol. 170:5
• Country of Publication: United States
• Language: English

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63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ESCHERICHIA COLI
RADIOSENSITIVITY
MUTATIONS
RADIOINDUCTION
NUCLEASES
ENZYME ACTIVITY
GENES
DNA REPAIR
GENE RECOMBINATION
PHENOTYPE
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ENZYMES
ESTERASES
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PHOSPHODIESTERASES
RADIATIONS
RECOVERY
REPAIR
560130* - Radiation Effects on Microorganisms