title: Structure analysis of the membrane-bound PhoD signal peptide of the Tat translocase shows an N-terminal amphiphilic helix.
abstract: Tat signal peptides provide the key signature for proteins that get exported by the bacterial twin arginine translocase. We have characterized the structure of the PhoD signal peptide from Bacillus subtilis in suitable membrane-mimicking environments. High-resolution ¹³C/¹⁵N NMR analysis in detergent micelles revealed a helical stretch in the signal peptide between positions 5 and 15, in good agreement with secondary structure prediction and circular dichroism results. This helix was found to be aligned parallel to the membrane surface according to oriented circular dichroism experiments carried out with planar lipid bilayers. The N-terminal α-helix exhibits a pronounced amphiphilic character, in contrast to the general view in the literature. So far, signal sequences had been supposed to consist of a positively charged N-terminal domain, followed by an α-helical hydrophobic segment, plus a C-terminal domain carrying the peptidase cleavage site. Based on our new structural insights, we propose a model for the folding and membrane interactions of the Tat signal sequence from PhoD.
authors.affiliation: Karlsruhe Institute of Technology, Institute of Organic Chemistry and CFN, Germany.
authors.forename: Marco J
authors.initials: MJ
authors.lastname: Klein
authors.forename: Stephan L
authors.initials: SL
authors.lastname: Grage
authors.forename: Claudia
authors.initials: C
authors.lastname: Muhle-Goll
authors.forename: Jochen
authors.initials: J
authors.lastname: Bürck
authors.forename: Sergii
authors.initials: S
authors.lastname: Afonin
authors.forename: Anne S
authors.initials: AS
authors.lastname: Ulrich
mesh_terms: D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000737:chemistry*; D002462:Cell Membrane / Q000737:chemistry* / Q000648:ultrastructure; D002942:Circular Dichroism; D008051:Lipid Bilayers; D026901:Membrane Transport Proteins / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D010458:Peptidyl Transferases / Q000737:chemistry*; D017510:Protein Folding; D021382:Protein Sorting Signals; D017433:Protein Structure, Secondary; D015398:Signal Transduction
chemical_list: D008051:Lipid Bilayers; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; D010458:Peptidyl Transferases