title: Isolation of exonuclease VIII: the enzyme associated with sbcA indirect suppressor.
abstract: recB and/or recC deficiency in Escherichia coli K-12 is indirectly suppressed by the presence of sbcA(-) mutations. sbcA(-) strains contain an increased level of an ATP-independent nuclease. Genetic and enzymatic tests indicate that this activity is not exonuclease III, exonuclease V (recB-recC nuclease), DNA polymerase I, or lambda exonuclease. This new enzyme (exonuclease VIII) has been purified 750-fold and shows a striking preference for double-stranded DNA over heat-denatured DNA. It does not act endonucleolytically on closed circular, single-stranded DNA as exonuclease V does. It also lacks a 3'-phosphatase function. Analysis on sodium dodecyl sulfate-polyacrylamide gels indicates that exonuclease VIII is not present in unsuppressed (sbcA(+)) strains. It is thought that sbcA determines some type of control function; the structural gene for exonuclease VIII is denoted by recE.
mesh_terms: D002848:Chromatography, DEAE-Cellulose; D004277:DNA, Single-Stranded / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000201:enzymology*; D005092:Exonucleases / Q000276:immunology / Q000302:isolation & purification*; D005796:Genes; D006868:Hydrolysis; D009154:Mutation; D009691:Nucleic Acid Denaturation; D011995:Recombination, Genetic; D013489:Suppression, Genetic; D014461:Ultracentrifugation
chemical_list: D004277:DNA, Single-Stranded; D005092:Exonucleases