title: Flp ribonuclease activities. Mechanistic similarities and contrasts to site-specific DNA recombination.
abstract: The ribonuclease active site harbored by the Flp site-specific recombinase can act on two neighboring phosphodiester bonds to yield mechanistically distinct chain breakage reactions. One of the RNase reactions apparently proceeds via a covalent enzyme intermediate and targets the phosphodiester position involved in DNA recombination (Flp RNase I activity). The second activity (Flp RNase II) targets the phosphodiester immediately to the 3' side but appears not to involve an enzyme-linked intermediate. Flp RNase I is absolutely dependent upon Tyr-343 of Flp and is competitive with respect to the normal strand joining reaction. It can utilize the 2'-hydroxyl group from any one of the four ribonucleotides with comparable efficiencies in the cleavage reaction. On the other hand, the RNase II reaction mediated by Flp(Y343F) is specific for U and cannot utilize the 2'-hydroxyl group from ribo-A, -G, or -C under standard reaction conditions. The RNase II activity is also sensitive to the 3'-neighboring base. Although dT is functional, the activity is stimulated by U or U-2'-OMe. The Flp RNase II reaction effectively competes with the normal strand cleavage reaction mediated by Tyr-343, even though their phosphodiester targets are not the same.
authors.affiliation: Department of Microbiology, and Institute of Cell and Molecular Biology, University of Texas, Austin, Texas 78712, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Xu
authors.forename: Y T
authors.initials: YT
authors.lastname: Ahn
authors.forename: S
authors.initials: S
authors.lastname: Pathania
authors.forename: M
authors.initials: M
authors.lastname: Jayaram
mesh_terms: D004247:DNA / Q000378:metabolism; D004254:DNA Nucleotidyltransferases / Q000378:metabolism*; D008956:Models, Chemical; D009690:Nucleic Acid Conformation; D012313:RNA / Q000378:metabolism; D011995:Recombination, Genetic; D012265:Ribonucleotides / Q000378:metabolism; D013379:Substrate Specificity; D014443:Tyrosine / Q000378:metabolism
chemical_list: D012265:Ribonucleotides; D014443:Tyrosine; D012313:RNA; D004247:DNA; D004254:DNA Nucleotidyltransferases; C045119:FLP recombinase