title: Mechanism of exonuclease action of BAL 31 nuclease.
abstract: Two kinetically and molecularly distinct forms ('fast' (F) and 'slow' (S] of nuclease BAL 31 from Alteromonas espejiana effect the length reduction of linear duplex DNAs through a 3'----5'-directed exonuclease activity in conjunction with an endonuclease activity against the 5'-terminated single-stranded tails generated by the exonuclease activity. No evidence for a 5'----3' mode of exonuclease action was seen. Single-stranded DNA is degraded predominantly by the 3'----5' exonuclease action. There is a pronounced decrease, to roughly constant values, of the average lengths of the tails in partially digested duplexes at a constant extent of digestion with increasing nuclease concentration. This decrease correlates with an increasing extent of ligatability, in the absence of repair, under conditions favoring the joining of fully base-paired ends. The exonuclease action, at least against duplex substrates, is quasi-processive and removes approx. 18 and 28 nucleotides per productive enzyme-substrate encounter for the S and F species, respectively. The dependence on Ca2+ and Mg2+ concentrations of the activities has been determined.
authors.affiliation: Department of Biochemical and Biophysical Sciences, University of Houston, TX 77204-5500.
authors.forename: X G
authors.initials: XG
authors.lastname: Zhou
authors.forename: H B
authors.initials: HB
authors.lastname: Gray
mesh_terms: D001435:Bacteriophages / Q000235:genetics; D002118:Calcium / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004279:DNA, Viral / Q000187:drug effects*; D004706:Endodeoxyribonucleases / Q000494:pharmacology*; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D009691:Nucleic Acid Denaturation
chemical_list: D004279:DNA, Viral; D004706:Endodeoxyribonucleases; C038407:exonuclease Bal 31; D008274:Magnesium; D002118:Calcium