title: Purification and properties of magnesium- and manganese-dependent ribonucleases H from chick embryo.
abstract: Two RNases H, Mg2+- and Mn2+-dependent RNases H, are present in extracts of chick embryo. These RNases H can be separated by phosphocellulose column chromatography. Mg2+-dependent RNase H was purified over 900-fold and Mn2+-dependent RNase H over 1,700-fold from chick embryo extracts. The molecular weight of the purified Mg2+-dependent RNase H was about 40,000 and of the Mn2+-dependent RNase H about 120,000, when estimated by gel filtration. Mg2+-dependent RNase H exhibits maximal activity at pH 9.5, and requires 15 to 20 mM Mg2+ for maximal activity, whereas Mn2+-dependent RNase H is most active at pH 8.5, and is maximally active at the concentration of 0.4 mM Mn2+, and has some activity with Mg2+. Both enzymes require a sulfhydryl reagent for maximal activity. Mn2+-dependent RNase H was inhibited by o-phenanthroline, pyrophosphate, and those polyamines tested, whereas Mg2+-dependent enzyme was not, although it was inhibited by NaF. Both RNases H liberate a mixture of oligonucleotides with 5'-phosphate and 3'-hydroxyl termini endonucleolytically.
mesh_terms: D000645:Ammonium Sulfate; D000818:Animals; D002642:Chick Embryo; D002850:Chromatography, Gel / Q000379:methods; D002852:Chromatography, Ion Exchange / Q000379:methods; D004722:Endoribonucleases / Q000302:isolation & purification* / Q000378:metabolism; D007525:Isoelectric Focusing; D008274:Magnesium / Q000378:metabolism*; D008345:Manganese / Q000378:metabolism*; D008970:Molecular Weight; D016914:Ribonuclease H
chemical_list: D008345:Manganese; D004722:Endoribonucleases; D016914:Ribonuclease H; D008274:Magnesium; D000645:Ammonium Sulfate