title: Identification of a substrate domain that determines system specificity in mycobacterial type VII secretion systems.
abstract: Type VII secretion (T7S) systems are specialized machineries used by mycobacterial pathogens to transport important virulence factors across their highly hydrophobic cell envelope. There are up to five mycobacterial T7S systems, named ESX-1 to ESX-5, at least three of which specifically secrete a different subset of substrates. The T7S substrates or substrate complexes are defined by the general secretion motif YxxxD/E. However this motif does not determine system specificity. Here, we show that the substrate domain recognized by the EspG chaperone is the determinant factor for this specificity. We first show that the introduction of point mutations into the EspG1-binding domain of the ESX-1 substrate pair PE35/PPE68_1 affects their secretion. Subsequently, we demonstrate that replacing this domain by the EspG5-binding domain of the ESX-5 substrate PPE18 resulted in EspG5dependence and exclusive rerouting to the ESX-5 system. This rerouting of PE35/PPE68_1 to the ESX-5 system had a negative effect on the secretion of endogenous ESX-5 substrates.
authors.affiliation: Section Molecular Microbiology, Amsterdam Institute of Molecules, Medicines &Systems, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
authors.forename: Trang H
authors.initials: TH
authors.lastname: Phan
authors.affiliation: Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Roy
authors.initials: R
authors.lastname: Ummels
authors.affiliation: Section Molecular Microbiology, Amsterdam Institute of Molecules, Medicines &Systems, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.|Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Wilbert
authors.initials: W
authors.lastname: Bitter
authors.affiliation: Section Molecular Microbiology, Amsterdam Institute of Molecules, Medicines &Systems, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
authors.forename: Edith N G
authors.initials: EN
authors.lastname: Houben
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D009161:Mycobacterium / Q000502:physiology*; D009169:Mycobacterium tuberculosis / Q000502:physiology; D011485:Protein Binding; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D021381:Protein Transport; D013379:Substrate Specificity; D000069377:Type VII Secretion Systems / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D008869:Microtubule-Associated Proteins; D000069377:Type VII Secretion Systems