title: DNA endonucleases associated with the avian myeloblastosis virus DNA polymerase.
abstract: A DNA endonuclease, Endo-I, which cleaves superhelical DNAs, has been isolated from avian myeloblastosis virions stripped of their coats by mild detergent treatment. The enzyme has a broad pH optimum around 7.5-8.0 and requires Mg2+ for activity. A second endonuclease, Endo-II, with a requirement for Mn2+, also present in viral cores, copurified with avian myeloblastosis virus alpha beta DNA polymerase (reverse transcriptase, RNA-dependent DNA nucleotidyltransferase) and similarly cleaved superhelical DNAs. Heat denaturation and sodium fluoride and N-ethylmaleimide inhibition studies were carried out to demonstrate a possible relationship between the two endonucleases and the viral DNA polymerase and RNase H activities. It appears that Endo-II may be an intrinsic activity of the polymerase.
mesh_terms: D001354:Avian Leukosis Virus / Q000201:enzymology*; D009189:Avian Myeloblastosis Virus / Q000201:enzymology*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D003851:Deoxyribonucleases / Q000378:metabolism*; D004720:Endonucleases / Q000378:metabolism*; D004789:Enzyme Activation; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D010446:Peptide Fragments / Q000032:analysis; D012260:Ribonucleases / Q000378:metabolism
chemical_list: D010446:Peptide Fragments; D008345:Manganese; D004259:DNA-Directed DNA Polymerase; D003851:Deoxyribonucleases; D004720:Endonucleases; D012260:Ribonucleases; D008274:Magnesium