The Escherichia coli UV Endonuclease (Correndonuclease II)
An endonuclease from Escherichia coli which acts specifically upon UV-irradiated DNA (correndonuclease II) and is absent from the uvrA and uvrB mutants has been isolated and partially characterized. The enzyme is present in normal amounts in the uvrC mutant. It elutes from phosphocellulose at about 0.25 M potassium phosphate (pH 7.5) and passes through dialysis tubing. The enzyme binds tightly to UV-irradiated DNA but does not bind to unirradiated DNA. The enzyme incises irradiated DNA to the 5′ side of a pyrimidine dimer and leaves a 5′-phosphoryl terminus which can be resealed with polynucleotide ligase. The K m of the enzyme is about 1.5 X 10-8 M dimers. Endonucleolytic activity of the enzyme is inhibited by caffeine with a K I of about 10mM.
KeywordsCrude Extract Dialysis Tubing Micrococcus Luteus Graduate Department Filter Binding Assay
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