title: Characterization and membrane assembly of the TatA component of the Escherichia coli twin-arginine protein transport system.
abstract: Proteins bearing a signal peptide with a consensus twin-arginine motif are translocated via the Tat pathway, a multiprotein system consisting minimally of the integral inner membrane proteins TatA, TatB, and TatC. On a molar basis, TatA is the major pathway component. Here we show that TatA can be purified independently of the other Tat proteins as a 460 kDa homooligomeric complex. Homooligomer formation requires the amino-terminal membrane-anchoring domain of TatA. According to circular dichroism spectroscopy, approximately half of the TatA polypeptide forms alpha-helical secondary structure in both detergent solution and proteoliposomes. An expressed construct without the transmembrane segment is largely unstructured in aqueous solution but is able to insert into phospholipid monolayers and interacts with membrane bilayers. Protease accessibility experiments indicate that the extramembranous region of TatA is located at the cytoplasmic face of the cell membrane.
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom.
authors.forename: Ida
authors.initials: I
authors.lastname: Porcelli
authors.forename: Erik
authors.initials: E
authors.lastname: de Leeuw
authors.forename: Russell
authors.initials: R
authors.lastname: Wallis
authors.forename: Els
authors.initials: E
authors.lastname: van den Brink-van der Laan
authors.forename: Ben
authors.initials: B
authors.lastname: de Kruijff
authors.forename: B A
authors.initials: BA
authors.lastname: Wallace
authors.forename: Tracy
authors.initials: T
authors.lastname: Palmer
authors.forename: Ben C
authors.initials: BC
authors.lastname: Berks
mesh_terms: D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism*; D002942:Circular Dichroism; D019281:Dimerization; D010450:Endopeptidases / Q000378:metabolism / Q000494:pharmacology; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011510:Proteolipids / Q000737:chemistry
chemical_list: D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D021122:Protein Subunits; D011510:Proteolipids; C499697:TatA protein, E coli; C461379:TatC protein, E coli; C020485:proteoliposomes; C408585:twin-arginine translocase complex, E coli; D010450:Endopeptidases