DNA scanning mechanism of T4 endonuclease V. Effect of NaCl concentration on processive nicking activity

Journal Article · Fri Jul 25 04:00:00 EDT 1986 · J. Biol. Chem.; (United States)

OSTI ID:5121009

Gruskin, E A; Lloyd, R S

T4 endonuclease V is a pyrimidine dimer-specific endonuclease which generates incisions in DNA at the sites of pyrimidine dimers by a processive reaction mechanism. A model is presented in which the degree of processivity is directly related to the efficacy of the one-dimensional diffusion of endonuclease V on DNA by which the enzyme locates pyrimidine dimers. The modulation of the processive nicking activity of T4 endonuclease V on superhelical covalently closed circular DNA (form I) which contains pyrimidine dimers has been investigated as a function of the ionic strength of the reaction. Agarose gel electrophoresis was used to separate the three topological forms of the DNA which were generated in time course reactions of endonuclease V with dimer-containing form I DNA in the absence of NaCl, and in 25, 50, and 100 mM NaCl. The degree of processivity was evaluated in terms of the mass fraction of form III (linear) DNA which was produced as a function of the fraction of form I DNA remaining. Processivity is maximal in the absence of NaCl and decreases as the NaCl concentration is increased. At 100 mM NaCl, processivity is abolished and endonuclease V generates incisions in DNA at the site of dimers by a distributive reaction mechanism. The change from the distributive to a processive reaction mechanism occurs at NaCl concentrations slightly below 50 mM. The high degree of processivity which is observed in the absence of NaCl is reversible to the distributive mechanism, as demonstrated by experiments in which the NaCl concentration was increased during the time course reaction. In addition, unirradiated DNA inhibited the incision of irradiated DNA only at NaCl concentrations at which processivity was observed.

• Research Organization: Vanderbilt Univ. School of Medicine, Nashville, TN
• OSTI ID: 5121009
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 21; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

560111* -- Radiation Effects on Biochemicals-- In Vitro-- (-1987)
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ALKALI METAL COMPOUNDS
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL PATHWAYS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CHLORIDES
CHLORINE COMPOUNDS
DNA
DNA REPAIR
DNA-ASE
ENDONUCLEASES
ENZYMES
ESTERASES
HALIDES
HALOGEN COMPOUNDS
HYDROLASES
IRRADIATION
KINETICS
MATHEMATICAL MODELS
NUCLEIC ACIDS
ORGANIC COMPOUNDS
PHOSPHODIESTERASES
POLYMERS
PYRIMIDINE DIMERS
REACTION KINETICS
RECOVERY
REPAIR
SODIUM CHLORIDES
SODIUM COMPOUNDS