tailieunhanh - Báo cáo sinh học: "Bridge helix and trigger loop perturbations generate superactive RNA polymerases"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học Journal of Biology đề tài: Bridge helix and trigger loop perturbations generate superactive RNA polymerases. | Journal of Biology BioMed Central Research article Open Access Bridge helix and trigger loop perturbations generate superactive RNA polymerases Lin Tan Simone Wiesler Dominika Trzaska Hannah C Carney and Robert OJ Weinzierl Address Department of Life Sciences Imperial College London Sir Alexander Fleming Building Exhibition Road London SW7 2AZ UK. Correspondence Robert OJ Weinzierl. Email Published 2 December 2008 Received 12 August 2008 Revised 24 September 2008 Journal of Biology 2008 7 40 doi jbiol98 J gy v J Accepted 31October 2008 The electronic version of this article is the complete one and can be found online at http content 7 10 40 2008 Tan et al. licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License http licenses by which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited. Abstract Background Cellular RNA polymerases are highly conserved enzymes that undergo complex conformational changes to coordinate the processing of nucleic acid substrates through the active site. Two domains in particular the bridge helix and the trigger loop play a key role in this mechanism by adopting different conformations at various stages of the nucleotide addition cycle. The functional relevance of these structural changes has been difficult to assess from the relatively small number of static crystal structures currently available. Results Using a novel robotic approach we characterized the functional properties of 367 site-directed mutants of the Methanocaldococcus jannaschii RNA polymerase A subunit revealing a wide spectrum of in vitro phenotypes. We show that a surprisingly large number of single amino acid substitutions in the bridge helix including a kink-inducing proline substitution increase the specific activity of RNA polymerase. Other superactivating .