title: Cord factor (trehalose 6,6'-dimycolate) forms fully stable and non-permeable lipid bilayers required for a functional outer membrane.
abstract: Cord factor (trehalose 6,6'-dimycolate, TDM) is the major lipid in the outer membrane of Corynebacteria and Mycobacteria. Although its role is well recognized in the immune response phenomena, its membrane biophysical properties remained largely unexplored and TDM has often been described as a detergent. We purified the main components of the outer membrane from Corynebacterium glutamicum and analyzed their membrane forming properties. In mixture with endogenous cardiolipin, but not alone, the spontaneous hydration of TDM produces liposomes. As a pure component, TDM formed vesicles only by the detergent dialysis method. Perdeuterated cardiolipin-TDM mixtures were shown by deuterium nuclear magnetic resonance (NMR) to exhibit a gel to liquid crystalline phase transition over a 273-295K temperature range, for cells grown at 303K, and thus to be in a liquid crystalline state at physiological temperature. Molecular dynamics simulations of hydrated TDM bilayers provided the trehalose average orientation and conformation, the chain order parameters, the area per lipid and the bilayer thickness which was confirmed by electron microscopy. Finally the Porin A-Porin H ion channel from the Corynebacterial outer membrane was reconstituted in TDM liposomes. With properly mycoloylated proteins, it manifested the typical voltage dependent ion channel properties of an outer membrane porin.
authors: Institute of Pharmacology and Structural Biology, Université de Toulouse, UPS, 205 route de Narbonne, 31077 Toulouse, France. rathparthasarathi@gmail.com
authors: Parthasarathi
authors: P
authors: Rath
authors: Olivier
authors: O
authors: Saurel
authors: Georges
authors: G
authors: Czaplicki
authors: Maryelle
authors: M
authors: Tropis
authors: Mamadou
authors: M
authors: Daffé
authors: Alexandre
authors: A
authors: Ghazi
authors: Pascal
authors: P
authors: Demange
authors: Alain
authors: A
authors: Milon
mesh_terms: D002308:Cardiolipins / Q000737:chemistry; D002462:Cell Membrane / Q000737:chemistry* / Q000648:ultrastructure; D003311:Cord Factors / Q000737:chemistry* / Q000302:isolation & purification; D048230:Corynebacterium glutamicum / Q000737:chemistry; D003903:Deuterium; D007473:Ion Channels / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry* / Q000648:ultrastructure; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D062105:Molecular Docking Simulation; D044367:Phase Transition; D018272:Porins / Q000737:chemistry* / Q000302:isolation & purification; D013696:Temperature
chemical_list: D002308:Cardiolipins; D003311:Cord Factors; D007473:Ion Channels; D008051:Lipid Bilayers; D008081:Liposomes; D018272:Porins; D003903:Deuterium
keywords: (2)H NMR; CL; Cardiolipin; DLS; EM; Ion channel; MD; Molecular dynamics simulation; Mycolic acid; OG; PG; PI; PIMs; Phase transition; Phosphatidylglycerol; Phosphatidylinositol; Phosphatidylinositol-mannosides; PorA–PorH; TDM; TMM; TOF; cardiolipin; dynamic light scattering; electron microscopy; major outer membrane protein complex from Corynebacterium glutamicum; molecular dynamics; n-octyl-β-d-glucopyranoside; time-of-flight; trehalose 6,6′-dimycolate; trehalose-monomycolate