title: Activation and repression of the activity of a lead ribozyme by the combination of Pb2+ and Mg2+.
abstract: The effect of Pb2+ and Mg2+ on the activity of a lead ribozyme with modified sequences has been studied. At low Pb2+ concentrations, cleavage at a previously reported site (site a) is observed. At higher Pb2+ concentrations, cleavage at a new site (site b) adjacent to site a is observed, while the cleavage at site a is repressed. On the addition of a certain amount of Mg2+, the cleavage at site a is enhanced by almost fourfold, while the cleavage at site b is repressed. Further addition of Mg2+ represses the cleavage at both sites. CD analysis indicates that the structure and stability of the lead ribozyme change depending on the metal conditions. Activation and repression of the activity by the combination of Pb2+ and Mg2+ are rationalized by considering that the two metals compete with each other for binding at two metal-binding sites.
authors.affiliation: Department of Bioengineering, Faculty of Engineering, Yokohama National University.
authors.forename: M H
authors.initials: MH
authors.lastname: Kim
authors.forename: M
authors.initials: M
authors.lastname: Katahira
authors.forename: T
authors.initials: T
authors.lastname: Sugiyama
authors.forename: S
authors.initials: S
authors.lastname: Uesugi
mesh_terms: D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002413:Cations, Divalent; D002942:Circular Dichroism; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D004794:Enzyme Repression / Q000187:drug effects; D004795:Enzyme Stability; D007854:Lead / Q000378:metabolism* / Q000494:pharmacology; D008274:Magnesium / Q000378:metabolism* / Q000494:pharmacology; D016337:RNA, Catalytic / Q000096:biosynthesis* / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D002413:Cations, Divalent; D016337:RNA, Catalytic; D007854:Lead; D008274:Magnesium