title: ESAT-6 from Mycobacterium tuberculosis dissociates from its putative chaperone CFP-10 under acidic conditions and exhibits membrane-lysing activity.
abstract: The 6-kDa early secreted antigenic target ESAT-6 and the 10-kDa culture filtrate protein CFP-10 of Mycobacterium tuberculosis are secreted by the ESX-1 system into the host cell and thereby contribute to pathogenicity. Although different studies performed at the organismal and cellular levels have helped to explain ESX-1-associated phenomena, not much is known about how ESAT-6 and CFP-10 contribute to pathogenesis at the molecular level. In this study we describe the interaction of both proteins with lipid bilayers, using biologically relevant liposomal preparations containing dimyristoylphosphatidylcholine (DMPC), dimyristoylphosphatidylglycerol, and cholesterol. Using flotation gradient centrifugation, we demonstrate that ESAT-6 showed strong association with liposomes, and in particular with preparations containing DMPC and cholesterol, whereas the interaction of CFP-10 with membranes appeared to be weaker and less specific. Most importantly, binding to the biomembranes no longer occurred when the proteins were present as a 1:1 ESAT-6.CFP-10 complex. However, lowering of the pH resulted in dissociation of the protein complex and subsequent protein-liposome interaction. Finally, cryoelectron microscopy revealed that ESAT-6 destabilized and lysed liposomes, whereas CFP-10 did not. In conclusion, we propose that one of the main features of ESAT-6 in the infection process of M. tuberculosis is the interaction with biomembranes that occurs after dissociation from its putative chaperone CFP-10 under acidic conditions typically encountered in the phagosome.
authors.affiliation: Unité de Génétique Moléculaire Bactérienne, Institut Pasteur, Paris, France.
authors.forename: Marien I
authors.initials: MI
authors.lastname: de Jonge
authors.forename: Gérard
authors.initials: G
authors.lastname: Pehau-Arnaudet
authors.forename: Marjan M
authors.initials: MM
authors.lastname: Fretz
authors.forename: Felix
authors.initials: F
authors.lastname: Romain
authors.forename: Daria
authors.initials: D
authors.lastname: Bottai
authors.forename: Priscille
authors.initials: P
authors.lastname: Brodin
authors.forename: Nadine
authors.initials: N
authors.lastname: Honoré
authors.forename: Gilles
authors.initials: G
authors.lastname: Marchal
authors.forename: Wim
authors.initials: W
authors.lastname: Jiskoot
authors.forename: Patrick
authors.initials: P
authors.lastname: England
authors.forename: Stewart T
authors.initials: ST
authors.lastname: Cole
authors.forename: Roland
authors.initials: R
authors.lastname: Brosch
mesh_terms: D000143:Acids / Q000494:pharmacology*; D000942:Antigens, Bacterial / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D018832:Molecular Chaperones; D009169:Mycobacterium tuberculosis / Q000737:chemistry / Q000378:metabolism*; D010587:Phagocytosis
chemical_list: D000143:Acids; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C117940:CFP-10 protein, Mycobacterium tuberculosis; C093276:ESAT-6 protein, Mycobacterium tuberculosis; D018832:Molecular Chaperones