title: Fatty acyl chains of Mycobacterium marinum lipooligosaccharides: structure, localization and acylation by PapA4 (MMAR_2343) protein.
abstract: We have recently established the fine structure of the glycan backbone of lipooligosaccharides (LOS-I to LOS-IV) isolated from Mycobacterium marinum, a close relative of Mycobacterium tuberculosis. These studies culminated with the description of an unusual terminal N-acylated monosaccharide that confers important biological functions to LOS-IV, such as macrophage activation, that may be relevant to granuloma formation. It was, however, also suggested that the lipid moiety was required for LOSs to exert their immunomodulatory activity. Herein, using highly purified LOSs from M. marinum, we have determined through a combination of mass spectrometric and NMR techniques, the structure and localization of the fatty acids composing the lipid moiety. The occurrence of two distinct polymethyl-branched fatty acids presenting specific localizations is consistent with the presence of two highly related polyketide synthases (Pks5 and Pks5.1) in M. marinum and presumably involved in the synthesis of these fatty acyl chains. In addition, a bioinformatic search permitted us to identify a set of enzymes potentially involved in the biosynthesis or transfer of these lipids to the LOS trehalose unit. These include MMAR_2343, a member of the Pap (polyketide-associated protein) family, that acylates trehalose-based glycolipids in M. marinum. The participation of MMAR_2343 to LOS assembly was demonstrated using a M. marinum mutant carrying a transposon insertion in the MMAR_2343 gene. Disruption of MMAR_2343 resulted in a severe LOS breakdown, indicating that MMAR_2343, hereafter designated PapA4, fulfills the requirements for LOS acylation and assembly.
authors.affiliation: Université de Lille 1, Unité de Glycobiologie Structurale et Fonctionnelle, F-59650 Villeneuve d'Ascq, France.
authors.forename: Yoann
authors.initials: Y
authors.lastname: Rombouts
authors.forename: Laeticia
authors.initials: L
authors.lastname: Alibaud
authors.forename: Séverine
authors.initials: S
authors.lastname: Carrère-Kremer
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Maes
authors.forename: Caroline
authors.initials: C
authors.lastname: Tokarski
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Elass
authors.forename: Laurent
authors.initials: L
authors.lastname: Kremer
authors.forename: Yann
authors.initials: Y
authors.lastname: Guérardel
mesh_terms: D000215:Acylation; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D019295:Computational Biology; D005227:Fatty Acids / Q000737:chemistry* / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D020868:Gene Silencing; D005798:Genes, Bacterial / Q000235:genetics; D008070:Lipopolysaccharides / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D019910:Mycobacterium marinum / Q000235:genetics / Q000378:metabolism*; D020102:Mycobacterium smegmatis / Q000378:metabolism; D011522:Protons; D016415:Sequence Alignment; D014199:Trehalose / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D005227:Fatty Acids; D008070:Lipopolysaccharides; D011522:Protons; C023023:lipid-linked oligosaccharides; D014199:Trehalose