title: Identification of specific posttranslationalO-mycoloylations mediating protein targeting to the mycomembrane.
abstract: The outer membranes (OMs) of members of the Corynebacteriales bacterial order, also called mycomembranes, harbor mycolic acids and unusual outer membrane proteins (OMPs), including those with α-helical structure. The signals that allow precursors of such proteins to be targeted to the mycomembrane remain uncharacterized. We report here the molecular features responsible for OMP targeting to the mycomembrane ofCorynebacterium glutamicum, a nonpathogenic member of the Corynebacteriales order. To better understand the mechanisms by which OMP precursors were sorted inC. glutamicum, we first investigated the partitioning of endogenous and recombinant PorA, PorH, PorB, and PorC between bacterial compartments and showed that they were both imported into the mycomembrane and secreted into the extracellular medium. A detailed investigation of cell extracts and purified proteins by top-down MS, NMR spectroscopy, and site-directed mutagenesis revealed specific and well-conserved posttranslational modifications (PTMs), includingO-mycoloylation, pyroglutamylation, andN-formylation, for mycomembrane-associated and -secreted OMPs. PTM site sequence analysis fromC. glutamicumOMP and otherO-acylated proteins in bacteria and eukaryotes revealed specific patterns. Furthermore, we found that such modifications were essential for targeting to the mycomembrane and sufficient for OMP assembly into mycolic acid-containing lipid bilayers. Collectively, it seems that these PTMs have evolved in the Corynebacteriales order and beyond to guide membrane proteins toward a specific cell compartment.
authors.affiliation: Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, Université Paul Sabatier, 31000 Toulouse, France.
authors.forename: Clément
authors.initials: C
authors.lastname: Carel
authors.affiliation: Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, Université Paul Sabatier, 31000 Toulouse, France.
authors.forename: Julien
authors.identifier: 0000-0001-7321-7436
authors.initials: J
authors.lastname: Marcoux
authors.affiliation: Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, Université Paul Sabatier, 31000 Toulouse, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Réat
authors.affiliation: Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, Université Paul Sabatier, 31000 Toulouse, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Parra
authors.affiliation: Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, Université Paul Sabatier, 31000 Toulouse, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Latgé
authors.affiliation: Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, Université Paul Sabatier, 31000 Toulouse, France.
authors.forename: Françoise
authors.initials: F
authors.lastname: Laval
authors.affiliation: Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, Université Paul Sabatier, 31000 Toulouse, France.
authors.forename: Pascal
authors.identifier: 0000-0002-9572-9990
authors.initials: P
authors.lastname: Demange
authors.affiliation: Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, Université Paul Sabatier, 31000 Toulouse, France.
authors.forename: Odile
authors.initials: O
authors.lastname: Burlet-Schiltz
authors.affiliation: Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, Université Paul Sabatier, 31000 Toulouse, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Milon
authors.affiliation: Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, Université Paul Sabatier, 31000 Toulouse, France.
authors.forename: Mamadou
authors.initials: M
authors.lastname: Daffé
authors.affiliation: Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, Université Paul Sabatier, 31000 Toulouse, France.
authors.forename: Maryelle G
authors.initials: MG
authors.lastname: Tropis
authors.affiliation: Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, Université Paul Sabatier, 31000 Toulouse, France marie.renault@ipbs.fr.
authors.forename: Marie A M
authors.initials: MAM
authors.lastname: Renault
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism*; D048230:Corynebacterium glutamicum / Q000254:growth & development / Q000378:metabolism*; D008051:Lipid Bilayers / Q000378:metabolism*; D009171:Mycolic Acids / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D017385:Sequence Homology
chemical_list: D001425:Bacterial Outer Membrane Proteins; D008051:Lipid Bilayers; D009171:Mycolic Acids
keywords: Corynebacteriales; NMR; O-acylation; sequence motif; top-down proteomics