title: Preferential chelation of cationic ligands to axial-equatorial oxygens over equatorial-equatorial dianionic oxygens: implication to the mechanism of action of ribozymes.
abstract: Effects of chelation of H2O, H+, and Mg2+ to two kinds of potential pentacoordinate intermediates of ribozyme reactions were investigated by ab initio molecular orbital calculations. Unexpectedly, in all cases examined, axial-equatorial chelations were found to be more stabilizing than equatorial-equatorial chelations. These results support the hypothesis that Mg2+ ion is bound to the equatorial phosphoryl oxygen and the axial leaving/attacking oxygen in the transition state of ribozyme reactions.
authors.affiliation: Fermentation Research Institute, Agency of Industrial Science & Technology, MITI, Tsukuba Science City, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Uebayasi
authors.forename: T
authors.initials: T
authors.lastname: Uchimaru
authors.forename: K
authors.initials: K
authors.lastname: Tanabe
authors.forename: S
authors.initials: S
authors.lastname: Nishikawa
authors.forename: K
authors.initials: K
authors.lastname: Taira
mesh_terms: D000838:Anions; D002412:Cations; D002614:Chelating Agents; D008024:Ligands; D008274:Magnesium / Q000737:chemistry; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry*; D016337:RNA, Catalytic / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D000838:Anions; D002412:Cations; D002614:Chelating Agents; D008024:Ligands; D016337:RNA, Catalytic; D008274:Magnesium; D010100:Oxygen