title: Effect of Zn2+ binding and enzyme active site on the transition state for RNA 2'-O-transphosphorylation interpreted through kinetic isotope effects.
abstract: Divalent metal ions, due to their ability to stabilize high concentrations of negative charge, are important for RNA folding and catalysis. Detailed models derived from the structures and kinetics of enzymes and from computational simulations have been developed. However, in most cases the specific catalytic modes involving metal ions and their mechanistic roles and effects on transition state structures remain controversial. Valuable information about the nature of the transition state is provided by measurement of kinetic isotope effects (KIEs). However, KIEs reflect changes in all bond vibrational modes that differ between the ground state and transition state. QM calculations are therefore essential for developing structural models of the transition state and evaluating mechanistic alternatives. Herein, we present computational models for Zn2+ binding to RNA 2'O-transphosphorylation reaction models that aid in the interpretation of KIE experiments. Different Zn2+ binding modes produce distinct KIE signatures, and one binding mode involving two zinc ions is in close agreement with KIEs measured for non-enzymatic catalysis by Zn2+ aquo ions alone. Interestingly, the KIE signatures in this specific model are also very close to those in RNase A catalysis. These results allow a quantitative connection to be made between experimental KIE measurements and transition state structure and bonding, and provide insight into RNA 2'O-ransphosphorylation reactions catalyzed by metal ions and enzymes. This article is part of a Special Issue entitled: Enzyme Transition States from Theory and Experiment.
authors: Center for Integrative Proteomics Research, BioMaPS Institute for Quantitative Biology, Rutgers University, Piscataway, NJ 08854, United States; Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, United States.
authors: Haoyuan
authors: H
authors: Chen
authors: Department of Chemistry, Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, United States.
authors: Joseph A
authors: JA
authors: Piccirilli
authors: Department of Biochemistry, Center for Proteomics and Bioinformatics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States.
authors: Michael E
authors: ME
authors: Harris
authors: Department of Biochemistry, Center for Proteomics and Bioinformatics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States. Electronic address: york@biomaps.rutgers.edu.
authors: Darrin M
authors: DM
authors: York
mesh_terms: D001665:Binding Sites; D055162:Biocatalysis; D020134:Catalytic Domain; D007554:Isotopes / Q000737:chemistry; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D010103:Oxygen Isotopes / Q000737:chemistry; D010766:Phosphorylation; D011485:Protein Binding; D012313:RNA / Q000737:chemistry* / Q000378:metabolism; D012259:Ribonuclease, Pancreatic / Q000737:chemistry* / Q000378:metabolism; D013379:Substrate Specificity; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism
chemical_list: D007554:Isotopes; D010103:Oxygen Isotopes; D012313:RNA; D012259:Ribonuclease, Pancreatic; D015032:Zinc
keywords: Enzyme; Kinetic isotope effect; Transition state; Transphosphorylation; Zn(2+) binding