title: Polar assembly and scaffolding proteins of the virulence-associated ESX-1 secretory apparatus in mycobacteria.
abstract: The ESX-1 secretion system is required for pathogenicity of Mycobacterium tuberculosis (Mtb). Despite considerable research, little is known about the structural components of ESX-1, or how these proteins are assembled into the active secretion apparatus. Here, we exploit the functionally related ESX-1 apparatus of Mycobacterium smegmatis (Ms) to show that fluorescently tagged proteins required for ESX-1 activity consistently localize to the cell pole, identified by time-lapse fluoro-microscopy as the non-septal (old) pole. Deletions in Msesx1 prevented polar localization of tagged proteins, indicating the need for specific protein-protein interactions in polar trafficking. Remarkably, expression of the Mtbesx1 locus in Msesx1 mutants restored polar localization of tagged proteins, indicating establishment of the MtbESX-1 apparatus in M. smegmatis. This observation illustrates the cross-species conservation of protein interactions governing assembly of ESX-1, as well as polar localization. Importantly, we describe novel non-esx1-encoded proteins, which affect ESX-1 activity, which colocalize with ESX-1, and which are required for ESX-1 recruitment and assembly. This analysis provides new insights into the molecular assembly of this important determinant of Mtb virulence.
authors.affiliation: Division of Genetics, Wadsworth Center, Center for Medical Science, New York State Department of Health, Albany, NY 12201, USA.
authors.forename: Samantha E
authors.initials: SE
authors.lastname: Wirth
authors.forename: Janet A
authors.initials: JA
authors.lastname: Krywy
authors.forename: Bree B
authors.initials: BB
authors.lastname: Aldridge
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Fortune
authors.forename: Marta
authors.initials: M
authors.lastname: Fernandez-Suarez
authors.forename: Todd A
authors.initials: TA
authors.lastname: Gray
authors.forename: Keith M
authors.initials: KM
authors.lastname: Derbyshire
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D058947:Bacterial Secretion Systems; D020102:Mycobacterium smegmatis / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D009876:Operon; D021381:Protein Transport; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems