title: Functional Tat transport of unstructured, small, hydrophilic proteins.
abstract: The twin-arginine translocation (Tat) system is a protein translocation system that is adapted to the translocation of folded proteins across biological membranes. An understanding of the folding requirements for Tat substrates is of fundamental importance for the elucidation of the transport mechanism. We now demonstrate for the first time Tat transport for fully unstructured proteins, using signal sequence fusions to naturally unfolded FG repeats from the yeast Nsp1p nuclear pore protein. The transport of unfolded proteins becomes less efficient with increasing size, consistent with only a single interaction between the system and the substrate. Strikingly, the introduction of six residues from the hydrophobic core of a globular protein completely blocked translocation. Physiological data suggest that hydrophobic surface patches abort transport at a late stage, most likely by membrane interactions during transport. This study thus explains the observed restriction of the Tat system to folded globular proteins on a molecular level.
authors.affiliation: Institute of Biology/Microbiology, University of Halle-Wittenberg, Kurt-Mothes-Strasse 3, D-06120 Halle, Germany.
authors.forename: Silke
authors.initials: S
authors.lastname: Richter
authors.affiliation: Institute of Biology/Microbiology, University of Halle-Wittenberg, Kurt-Mothes-Strasse 3, D-06120 Halle, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Lindenstrauss
authors.affiliation: Max Planck Research Unit for Enzymology of Protein Folding, Weinbergweg 22, D-06120 Halle, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Lücke
authors.affiliation: Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, United Kingdom.
authors.forename: Richard
authors.initials: R
authors.lastname: Bayliss
authors.affiliation: Institute of Biology/Microbiology, University of Halle-Wittenberg, Kurt-Mothes-Strasse 3, D-06120 Halle, Germany. Electronic address: t.brueser@mikrobiologie.uni-halle.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Brüser
mesh_terms: D002135:Calcium-Binding Proteins / Q000737:chemistry; D002462:Cell Membrane / Q000378:metabolism; D003062:Codon; D017931:DNA Primers / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry; D015696:Gene Products, tat / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D009154:Mutation; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011489:Protein Denaturation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry
chemical_list: D002135:Calcium-Binding Proteins; D003062:Codon; D017931:DNA Primers; D005656:Fungal Proteins; D015696:Gene Products, tat; D008024:Ligands; C062748:NSP1 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins