title: 'In-line attack' conformational effect plays a modest role in an enzyme-catalyzed RNA cleavage: a free energy simulation study.
abstract: Since the proposal of 'in-line attack' conformation as a possibly important intermediate in RNA cleavage, its structure has been captured in various protein and RNA enzymes; these structures strengthen the belief that this conformation plays an essential role in the catalysis of RNA cleavage. As generally discussed, this intermediate structure can be involved in energy barrier reduction in two possible ways, e.g. through either conformational effect or electrostatic effect. In order to quantitatively elucidate the contribution of conformational effect in this type of enzyme catalysis, free energy simulations were performed on the RNA structures both in a splicing endonuclease complex and in the aqueous solution. Our free energy simulation results revealed that the 'in-line attack' conformational effect plays a modest role in facilitating the reaction rate enhancement (approximately 12-fold) compared with the overall 10(12)-fold rate increase. The close agreement between the present computational estimation and an experimental measurement on the spontaneous RNA cleavage in an in vitro evolved ATP aptamer motives us to realize that the conformation distribution of an enzyme substrate prior to rather than after its binding determines the upper bound of the rate enhancement ability through the conformational strategy.
authors.affiliation: School of Computational Science, Florida State University, Tallahassee, FL 32306, USA.
authors.forename: Donghong
authors.initials: D
authors.lastname: Min
authors.forename: Song
authors.initials: S
authors.lastname: Xue
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
mesh_terms: D002384:Catalysis; D019295:Computational Biology; D003198:Computer Simulation; D004722:Endoribonucleases / Q000737:chemistry*; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D012313:RNA / Q000737:chemistry* / Q000378:metabolism; D055672:Static Electricity
chemical_list: D012313:RNA; D004722:Endoribonucleases; C051012:splicing endonuclease