The (A)BC excinuclease of Escherichia coli has only the UvrB and UvrC subunits in the incision complex

Journal Article · Sat Jul 01 00:00:00 EDT 1989 · Proceedings of the National Academy of Sciences of the United States of America; (USA)

DOI:https://doi.org/10.1073/pnas.86.14.5237· OSTI ID:5560745

Orren, D K; Sancar, A ^[1]

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1. Univ. of North Carolina School of Medicine, Chapel Hill (USA)

The uvrA, uvrB, and uvrC genes control excision repair in Escherichia coli. Cells with mutations in any of these three genes cannot repair DNA by nucleotide excision. When the purified gene products--the UvrA, UvrB, and UvrC proteins--are mixed together, an excision nuclease is formed that incises on both sides of the damaged nucleotide in an ATP-dependent reaction; it has been presumed that the excision nuclease was an ABC complex containing all three Uvr proteins. To determine the stoichiometry of the subunits in the enzyme, we conducted hydrodynamic studies with mixtures of the subunits with or without DNA substrate. We found that without DNA the UvrA subunit is a dimer and that when UvrB protein is also present, a (UvrA)2(UvrB)1 complex forms. Without DNA no detectable interaction of either the UvrA or UvrB subunits or the (UvrA)2(UvrB)1 complex with the UvrC subunit occurs. Unexpectedly, with UV-irradiated DNA, the UvrA/UvrB ratio in isolated DNA-protein complexes is variable, and the ratio becomes infinitesimally low as the UvrA concentration in the reaction mixture decreases. Under conditions of saturating UvrB protein approximately one UvrB molecule binds to DNA per damaged site in a reaction that requires catalytic amounts of UvrA subunit. Addition of UvrC protein to purified UvrB-DNA complexes results in rapid incision of the DNA, presumably catalyzed by an excision nuclease containing only UvrB and UvrC subunits.

• OSTI ID: 5560745
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America; (USA), Journal Name: Proceedings of the National Academy of Sciences of the United States of America; (USA) Vol. 86:14; ISSN PNASA; ISSN 0027-8424
• 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.
ATP
BACTERIA
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CELL CONSTITUENTS
DNA
DNA REPAIR
ELECTROMAGNETIC RADIATION
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ESCHERICHIA COLI
ESTERASES
EXCISION REPAIR
GENE MUTATIONS
GENES
GENETIC EFFECTS
GENETIC RADIATION EFFECTS
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MICROORGANISMS
MOLECULAR WEIGHT
MUTATIONS
NUCLEASES
NUCLEIC ACIDS
NUCLEOTIDES
ORGANIC COMPOUNDS
PHOSPHODIESTERASES
PLASMIDS
PROTEINS
RADIATION EFFECTS
RADIATIONS
RADIOINDUCTION
RECOVERY
REPAIR
STOICHIOMETRY
ULTRAVIOLET RADIATION