title: Export pathway selectivity of Escherichia coli twin arginine translocation signal peptides.
abstract: The Escherichia coli genome encodes at least 29 putative signal peptides containing a twin arginine motif characteristic of proteins exported via the twin arginine translocation (Tat) pathway. Fusions of the putative Tat signal peptides plus six to eight amino acids of the mature proteins to three reporter proteins (short-lived green fluorescent protein, maltose-binding protein (MBP), and alkaline phosphatase) and also data from the cell localization of epitope-tagged full-length proteins were employed to determine the ability of the 29 signal peptides to direct export through the Tat pathway, through the general secretory pathway (Sec), or through both. 27/29 putative signal peptides could export one or more reporter proteins through Tat. Of these, 11 signal peptides displayed Tat specificity in that they could not direct the export of Sec-only reporter proteins. The rest (16/27) were promiscuous and were capable of directing export of the appropriate reporter either via Tat (green fluorescent protein, MBP) or via Sec (PhoA, MBP). Mutations that conferred a >or=+1 charge to the N terminus of the mature protein abolished or drastically reduced routing through the Sec pathway without affecting the ability to export via the Tat pathway. These experiments demonstrate that the charge of the mature protein N terminus affects export promiscuity, independent of the effect of the folding state of the mature protein.
authors.affiliation: Department of Chemical Engineering, Institute for Cell and Molecular Biology, University of Texas, Austin 78712, USA.
authors.forename: Danielle
authors.initials: D
authors.lastname: Tullman-Ercek
authors.forename: Matthew P
authors.initials: MP
authors.lastname: DeLisa
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Kawarasaki
authors.forename: Pooya
authors.initials: P
authors.lastname: Iranpour
authors.forename: Brian
authors.initials: B
authors.lastname: Ribnicky
authors.forename: Tracy
authors.initials: T
authors.lastname: Palmer
authors.forename: George
authors.initials: G
authors.lastname: Georgiou
mesh_terms: D000595:Amino Acid Sequence; D001692:Biological Transport; D019295:Computational Biology; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D016680:Genome, Bacterial; D049452:Green Fluorescent Proteins / Q000737:chemistry; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D017510:Protein Folding; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D013347:Subcellular Fractions
chemical_list: D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; C408585:twin-arginine translocase complex, E coli; D049452:Green Fluorescent Proteins