title: Characterization of a Mycobacterium tuberculosis nanocompartment and its potential cargo proteins.
abstract: Mycobacterium tuberculosis has evolved various mechanisms by which the bacterium can maintain homeostasis under numerous environmental assaults generated by the host immune response. M. tuberculosis harbors enzymes involved in the oxidative stress response that aid in survival during the production of reactive oxygen species in activated macrophages. Previous studies have shown that a dye-decolorizing peroxidase (DyP) is encapsulated by a bacterial nanocompartment, encapsulin (Enc), whereby packaged DyP interacts with Enc via a unique C-terminal extension. M. tuberculosis also harbors an encapsulin homolog (CFP-29, Mt-Enc), within an operon with M. tuberculosis DyP (Mt-DyP), which contains a C-terminal extension. Together these observations suggest that Mt-DyP interacts with Mt-Enc. Furthermore, it has been suggested that DyPs may function as either a heme-dependent peroxidase or a deferrochelatase. Like Mt-DyP, M. tuberculosis iron storage ferritin protein, Mt-BfrB, and an M. tuberculosis protein involved in folate biosynthesis, 7,8-dihydroneopterin aldolase (Mt-FolB), have C-terminal tails that could also interact with Mt-Enc. For the first time, we show by co-purification and electron microscopy that mycobacteria via Mt-Enc can encapsulate Mt-DyP, Mt-BfrB, and Mt-FolB. Functional studies of free or encapsulated proteins demonstrate that they retain their enzymatic activity within the Mt-Enc nanocompartment. Mt-DyP, Mt-FolB, and Mt-BfrB all have antioxidant properties, suggesting that if these proteins are encapsulated by Mt-Enc, then this nanocage may play a role in the M. tuberculosis oxidative stress response. This report provides initial structural and biochemical clues regarding the molecular mechanisms that utilize compartmentalization by which the mycobacterial cell may aid in detoxification of the local environment to ensure long term survival.
authors.affiliation: From the Departments of Molecular Biology and Biochemistry and.
authors.forename: Heidi
authors.initials: H
authors.lastname: Contreras
authors.affiliation: the Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, La Jolla, California 92037, and.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Joens
authors.affiliation: From the Departments of Molecular Biology and Biochemistry and.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: McMath
authors.affiliation: From the Departments of Molecular Biology and Biochemistry and.
authors.forename: Vincent P
authors.initials: VP
authors.lastname: Le
authors.affiliation: the Division of Infectious Diseases, Department of Medicine, School of Medicine, UCLA, Los Angeles, California 90095.
authors.forename: Michael V
authors.initials: MV
authors.lastname: Tullius
authors.affiliation: the Division of Infectious Diseases, Department of Medicine, School of Medicine, UCLA, Los Angeles, California 90095.
authors.forename: Jaqueline M
authors.initials: JM
authors.lastname: Kimmey
authors.affiliation: the Division of Infectious Diseases, Department of Medicine, School of Medicine, UCLA, Los Angeles, California 90095.
authors.forename: Neda
authors.initials: N
authors.lastname: Bionghi
authors.affiliation: the Division of Infectious Diseases, Department of Medicine, School of Medicine, UCLA, Los Angeles, California 90095.
authors.forename: Marcus A
authors.initials: MA
authors.lastname: Horwitz
authors.affiliation: the Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, La Jolla, California 92037, and.
authors.forename: James A J
authors.initials: JA
authors.lastname: Fitzpatrick
authors.affiliation: From the Departments of Molecular Biology and Biochemistry and Pharmaceutical Sciences, University of California, Irvine, California 92697, celia.goulding@uci.edu.
authors.forename: Celia W
authors.initials: CW
authors.lastname: Goulding
mesh_terms: D000446:Aldehyde-Lyases / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D015388:Organelles / Q000235:genetics / Q000378:metabolism*; D009195:Peroxidase / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D001426:Bacterial Proteins; D009195:Peroxidase; D000446:Aldehyde-Lyases; C020044:dihydroneopterin aldolase
keywords: Electron Microscopy (EM); Mycobacterium tuberculosis; Nanocompartments; Oxidative Stress; Protein Self-assembly; Protein-Protein Interaction