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

Journal Article · Sun May 01 04:00:00 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), Journal Name: J. Bacteriol.; (United States) Vol. 170:5; ISSN JOBAA
• Country of Publication: United States
• Language: English

Related Subjects

560130* -- Radiation Effects on Microorganisms
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BACTERIA
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
DNA
DNA REPAIR
ELECTROMAGNETIC RADIATION
ENZYME ACTIVITY
ENZYMES
ESCHERICHIA COLI
ESTERASES
GENE RECOMBINATION
GENES
HYDROLASES
MICROORGANISMS
MUTATIONS
NUCLEASES
NUCLEIC ACIDS
ORGANIC COMPOUNDS
PHENOTYPE
PHOSPHODIESTERASES
RADIATIONS
RADIOINDUCTION
RADIOSENSITIVITY
RECOMBINANT DNA
RECOVERY
REPAIR
ULTRAVIOLET RADIATION