tailieunhanh - Báo cáo khoa hoc : High-pressure analysis of a hammerhead ribozyme from Chrysanthemum chlorotic mottle viroid reveals two different populations of self-cleaving molecule

The activity of the full-length hammerhead ribozyme requires a tertiary interaction between its distal loops leading to the closure of the molecule and its stabilization in the active conformation. | IFEBS Journal High-pressure analysis of a hammerhead ribozyme from Chrysanthemum chlorotic mottle viroid reveals two different populations of self-cleaving molecule Hussein Kaddour1 Jacques Vergne1 Guy Herve2 and Marie-Christine Maurel1 1 Acides Nucleiques et Biophotonique CNRS FRE 3207 UPMC Université Paris 06 France 2 Laboratoire BIOSIPE CNRS and ER3 UPMC Universite Paris 06 France Keywords activation volume hammerhead ribozyme high pressure kinetics RNA Correspondence . Maurel Acides Nucleiques et Biophotonique ANbioPhy Universite Pierre et Marie Curie Tour 32 - 32-33 - 5eme etage 4 place Jussieu 75252 Paris Cedex 05 France Fax 33 144279916 Tel 33 144274021 E-mail Received 5 July 2011 revised 26 July 2011 accepted 3 August 2011 doi The activity of the full-length hammerhead ribozyme requires a tertiary interaction between its distal loops leading to the closure of the molecule and its stabilization in the active conformation. In this study the conformational changes accompanying the cis-cleavage reaction of Chrysanthemum chlorotic mottle viroid hammerhead ribozyme were investigated by high-pressure experiments on the complete cleavage reaction. Two activation volumes AV were measured pointing to the presence of two different populations of molecules corresponding to fast-cleaving and slow-cleaving ribozymes in the reaction mixture. The fast population with a small AV of mL-mol-1 most likely represents molecules in the nearactive conformation whereas the slow population with a larger AV of mL-mol-1 represents molecules that need a larger conformational change to induce activity. In addition pH-dependence experiments suggest that the group whose deprotonation is required for activity intervenes in the formation of the transition state or in the chemistry of the reaction but not in the conformational change that precedes it. Introduction The hammerhead ribozyme HHR is a small catalytic RNA

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