title: Structural characterization of the pore forming protein TatAd of the twin-arginine translocase in membranes by solid-state 15N-NMR.
abstract: The transmembrane protein TatA is the pore forming unit of the twin-arginine translocase (Tat), which has the unique ability of transporting folded proteins across the cell membrane. This ATP-independent protein export pathway is a recently discovered alternative to the general secretory (Sec) system of bacteria. To obtain insight in the translocation mechanism, the structure and alignment in the membrane of the well-folded segments 2-45 of TatAd from Bacillus subtilis was studied here. Using solid-state NMR in bicelles containing anionic lipids, the topology and orientation of TatAd was determined in an environment mimicking the bacterial membrane. A wheel-like pattern, characteristic for a tilted transmembrane helix, was observed in 15N chemical shift /15N-1H dipolar coupling correlation NMR spectra. Analysis of this PISA wheel revealed a 14-16 residue long N-terminal membrane-spanning helix which is tilted by 17 degrees with respect to the membrane normal. In addition, comparison of uniformly and selectively 15N-labeled TatA2-45 samples allowed determination of the helix polarity angle.
authors.affiliation: Forschungszentrum Karlsruhe, POB 3640, D-76021 Karlsruhe, Germany.
authors.forename: Sonja D
authors.initials: SD
authors.lastname: Müller
authors.forename: Anna A
authors.initials: AA
authors.lastname: De Angelis
authors.forename: Torsten H
authors.initials: TH
authors.lastname: Walther
authors.forename: Stephan L
authors.initials: SL
authors.lastname: Grage
authors.forename: Christian
authors.initials: C
authors.lastname: Lange
authors.forename: Stanley J
authors.initials: SJ
authors.lastname: Opella
authors.forename: Anne S
authors.initials: AS
authors.lastname: Ulrich
mesh_terms: D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003198:Computer Simulation; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data
chemical_list: D001426:Bacterial Proteins; D026901:Membrane Transport Proteins