title: An RTX transporter tethers its unfolded substrate during secretion via a unique N-terminal domain.
abstract: Type 1 secretion systems (T1SS) catalyze the one step protein transport across the membranes of Gram-negative bacteria and are composed of an outer membrane protein, a membrane fusion protein and an ABC transporter. The ABC transporter consists of the canonical nucleotide binding and transmembrane domains. For the toxin hemolysin A (HlyA), the ABC transporter HlyB carries an additional, N-terminal domain sharing about 40% homology to C39 peptidases, but this "C39-like domain" (CLD) is suggested to feature another, yet unknown function. Our functional and structural analysis demonstrates that the CLD is essential for secretion and that it specifically interacts with the unfolded state of HlyA. We determined the nuclear magnetic resonance structure of the CLD as well as the substrate-binding region within the CLD. This mode of action, represents a mechanism within T1SS and answers the question, how a large and unfolded substrate is protected inside the cells during secretion.
authors.affiliation: Institute of Physical Biology, Heinrich-Heine-Universität, Universitätsstrasse 1, 40225 Düsseldorf, Germany.
authors.forename: Justin
authors.initials: J
authors.lastname: Lecher
authors.forename: Christian K W
authors.initials: CK
authors.lastname: Schwarz
authors.forename: Matthias
authors.initials: M
authors.lastname: Stoldt
authors.forename: Sander H J
authors.initials: SH
authors.lastname: Smits
authors.forename: Dieter
authors.initials: D
authors.lastname: Willbold
authors.forename: Lutz
authors.initials: L
authors.lastname: Schmitt
mesh_terms: D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000302:isolation & purification / Q000378:metabolism; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D014364:Tryptophan / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C036507:Hlya protein, E coli; C050837:Hlyb protein, Bacteria; D010446:Peptide Fragments; D014364:Tryptophan