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Báo cáo khoa học: Intrinsic GTPase activity of a bacterial twin-arginine translocation proofreading chaperone induced by domain swapping

The bacterial twin-arginine translocation (Tat) system is a protein targeting pathway dedicated to the transport of folded proteins across the cytoplas-mic membrane. Proteins transported on the Tat pathway are synthesised as precursors with N-terminal signal peptides containing a conserved amino acid motif. | Intrinsic GTPase activity of a bacterial twin-arginine translocation proofreading chaperone induced by domain swapping David Guymer1 Julien Maillard2 Mark F. Agacan1 Charles A. Brearley3 and Frank Sargent1 1 College of Life Sciences University of Dundee Dundee UK 2 ENAC-ISTE Laboratoire de Biotechnologie Environnementale LBE EPF Lausanne Switzerland 3 Schoolof BiologicalSciences University of East Anglia Norwich UK Keywords Escherichia coli molecular chaperones noncanonicalGTPase TorD protein twin-arginine transport pathway Correspondence F. Sargent Division of Molecular Microbiology College of Life Sciences University of Dundee Dundee DD1 5EH UK Fax 44 1382 388 216 Tel 44 1382 386 463 E-mail f.sargent@dundee.ac.uk Received 28 July 2009 revised 12 November 2009 accepted 18 November 2009 doi 10.1111 j.1742-4658.2009.07507.x The bacterial twin-arginine translocation Tat system is a protein targeting pathway dedicated to the transport of folded proteins across the cytoplasmic membrane. Proteins transported on the Tat pathway are synthesised as precursors with N-terminal signal peptides containing a conserved amino acid motif. In Escherichia coli many Tat substrates contain prosthetic groups and undergo cytoplasmic assembly processes prior to the translocation event. A pre-export Tat proofreading process mediated by signal peptide-binding chaperones is considered to prevent premature export of some Tat-targeted proteins until all other assembly processes are complete. TorD is a paradigm Tat proofreading chaperone and co-ordinates the maturation and export of the periplasmic respiratory enzyme trimethylamine N-oxide reductase TorA . Although it is well established that TorD binds directly to the TorA signal peptide the mechanism of regulation or control of binding is not understood. Previous structural analyses of TorD homologues showed that these proteins can exist as monomeric and domainswapped dimeric forms. In the present study we demonstrate that isolated .