tailieunhanh - Báo cáo khoa học: Bioenergetic requirements of a Tat-dependent substrate in the halophilic archaeon Haloarcula hispanica

Twin-arginine translocase (Tat) is involved in the translocation of fully folded proteins in a process that is driven by the proton motive force. In most prokaryotes, the Tat system transports only a small proportion of secretory proteins, and Tat substrates are often cofactor-containing proteins that require folding before translocation. | Bioenergetic requirements of a Tat-dependent substrate in the halophilic archaeon Haloarcula hispanica Daniel C. Kwan1 Judith R. Thomas2 and Albert Bolhuis1 1 Department of Pharmacy and Pharmacology University of Bath UK 2 Department of BiologicalSciences University of Warwick Coventry UK Keywords halophilic archaea protein translocation signal peptide sodium motive force twin-arginine translocase Correspondence A. Bolhuis Department of Pharmacy and Pharmacology University of Bath Bath BA2 7AY UK Fax 44 1225 386114 Tel 44 1225 383813 E-mail Present address Systems Biology Laboratory UK Abingdon UK Twin-arginine translocase Tat is involved in the translocation of fully folded proteins in a process that is driven by the proton motive force. In most prokaryotes the Tat system transports only a small proportion of secretory proteins and Tat substrates are often cofactor-containing proteins that require folding before translocation. A notable exception is found in halophilic archaea haloarchaea which are predicted to secrete the majority of their proteins through the Tat pathway. In this study we have analysed the translocation of a secretory protein AmyH from the haloarchaeon Haloarcula hispanica. Using both in vivo and in vitro translocation assays we demonstrate that AmyH transport is Tat-dependent and surprisingly that its secretion does not depend on the proton motive force but requires the sodium motive force instead. Received 6 May 2008 revised 1 October 2008 accepted 13 October 2008 doi The twin-arginine translocation Tat pathway is a system for protein translocation that is found in the cytoplasmic membrane of most prokaryotes and in the thylakoid membrane of chloroplasts 1 . The Tat system usually requires two or three membrane-bound components denoted TatA TatB and TatC. TatA and TatB are similar in sequence and structure and contain one membrane-spanning domain whereas TatC contains six membrane-spanning