title: Composition of the type VII secretion system membrane complex.
abstract: Pathogenic mycobacteria require type VII secretion (T7S) systems to transport virulence factors across their complex cell envelope. These bacteria have up to five of these systems, termed ESX-1 to ESX-5. Here, we show that ESX-5 of Mycobacterium tuberculosis mediates the secretion of EsxN, PPE and PE_PGRS proteins, indicating that ESX-5 is a major secretion pathway in this important pathogen. Using the ESX-5 system of Mycobacterium marinum and Mycobacterium bovis BCG as a model, we have purified and analysed the T7S membrane complex under native conditions. blue native-PAGE and immunoprecipitation experiments showed that the ESX-5 membrane complex of both species has a size of ~ 1500 kDa and is composed of four conserved membrane proteins, i.e. EccB(5) , EccC(5) , EccD(5) and EccE(5) . Subsequent limited proteolysis suggests that EccC(5) and EccE(5) mostly reside on the periphery of the complex. We also observed that EccC(5) and EccD(5) expression is essential for the formation of a stable membrane complex. These are the first data on a T7S membrane complex and, given the high conservation of its components, our data can likely be generalized to most mycobacterial T7S systems.
authors.affiliation: Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, The Netherlands. e.houben@vumc.nl
authors.forename: Edith N G
authors.initials: EN
authors.lastname: Houben
authors.forename: Jovanka
authors.initials: J
authors.lastname: Bestebroer
authors.forename: Roy
authors.initials: R
authors.lastname: Ummels
authors.forename: Louis
authors.initials: L
authors.lastname: Wilson
authors.forename: Sander R
authors.initials: SR
authors.lastname: Piersma
authors.forename: Connie R
authors.initials: CR
authors.lastname: Jiménez
authors.forename: Tom H M
authors.initials: TH
authors.lastname: Ottenhoff
authors.forename: Joen
authors.initials: J
authors.lastname: Luirink
authors.forename: Wilbert
authors.initials: W
authors.lastname: Bitter
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D058947:Bacterial Secretion Systems; D002462:Cell Membrane / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019910:Mycobacterium marinum / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009169:Mycobacterium tuberculosis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems