title: Structure of the mycosin-1 protease from the mycobacterial ESX-1 protein type VII secretion system.
abstract: Mycobacteria use specialized type VII (ESX) secretion systems to export proteins across their complex cell walls. Mycobacterium tuberculosis encodes five nonredundant ESX secretion systems, with ESX-1 being particularly important to disease progression. All ESX loci encode extracellular membrane-bound proteases called mycosins (MycP) that are essential to secretion and have been shown to be involved in processing of type VII-exported proteins. Here, we report the first x-ray crystallographic structure of MycP1(24-407) to 1.86 Å, defining a subtilisin-like fold with a unique N-terminal extension previously proposed to function as a propeptide for regulation of enzyme activity. The structure reveals that this N-terminal extension shows no structural similarity to previously characterized protease propeptides and instead wraps intimately around the catalytic domain where, tethered by a disulfide bond, it forms additional interactions with a unique extended loop that protrudes from the catalytic core. We also show MycP1 cleaves the ESX-1 secreted protein EspB from both M. tuberculosis and Mycobacterium smegmatis at a homologous cut site in vitro.
authors.affiliation: Department of Biochemistry and Molecular Biology and Centre for Blood Research, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
authors.forename: Matthew
authors.initials: M
authors.lastname: Solomonson
authors.forename: Pitter F
authors.initials: PF
authors.lastname: Huesgen
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Wasney
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Watanabe
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Gruninger
authors.forename: Gerd
authors.initials: G
authors.lastname: Prehna
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Overall
authors.forename: Natalie C J
authors.initials: NC
authors.lastname: Strynadka
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D058947:Bacterial Secretion Systems; D020134:Catalytic Domain; D016384:Consensus Sequence; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020102:Mycobacterium smegmatis / Q000201:enzymology*; D009169:Mycobacterium tuberculosis; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary; D059748:Proteolysis; D017386:Sequence Homology, Amino Acid; D013381:Subtilisins / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D013381:Subtilisins
keywords: ESX; Microbiology; Mycobacteria; Mycobacterium tuberculosis; Protease; Protein Secretion; Subtilisin; Type VII Secretion System