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Hart EM, Lyerly E, Bernhardt TG. The conserved σD envelope stress response monitors multiple aspects of envelope integrity in corynebacteria. PLoS Genet 2024; 20:e1011127. [PMID: 38829907 PMCID: PMC11175481 DOI: 10.1371/journal.pgen.1011127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Revised: 06/13/2024] [Accepted: 05/15/2024] [Indexed: 06/05/2024] Open
Abstract
The cell envelope fortifies bacterial cells against antibiotics and other insults. Species in the Mycobacteriales order have a complex envelope that includes an outer layer of mycolic acids called the mycomembrane (MM) and a cell wall composed of peptidoglycan and arabinogalactan. This envelope architecture is unique among bacteria and contributes significantly to the virulence of pathogenic Mycobacteriales like Mycobacterium tuberculosis. Characterization of pathways that govern envelope biogenesis in these organisms is therefore critical in understanding their biology and for identifying new antibiotic targets. To better understand MM biogenesis, we developed a cell sorting-based screen for mutants defective in the surface exposure of a porin normally embedded in the MM of the model organism Corynebacterium glutamicum. The results revealed a requirement for the conserved σD envelope stress response in porin export and identified MarP as the site-1 protease, respectively, that activate the response by cleaving the membrane-embedded anti-sigma factor. A reporter system revealed that the σD pathway responds to defects in mycolic acid and arabinogalactan biosynthesis, suggesting that the stress response has the unusual property of being induced by activating signals that arise from defects in the assembly of two distinct envelope layers. Our results thus provide new insights into how C. glutamicum and related bacteria monitor envelope integrity and suggest a potential role for members of the σD regulon in protein export to the MM.
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Affiliation(s)
- Elizabeth M. Hart
- Department of Microbiology, Harvard Medical School, Boston, Massachusetts, United States of America
- Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Evan Lyerly
- Department of Microbiology, Harvard Medical School, Boston, Massachusetts, United States of America
- Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Thomas G. Bernhardt
- Department of Microbiology, Harvard Medical School, Boston, Massachusetts, United States of America
- Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts, United States of America
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Williams JT, Abramovitch RB. Molecular Mechanisms of MmpL3 Function and Inhibition. Microb Drug Resist 2023; 29:190-212. [PMID: 36809064 PMCID: PMC10171966 DOI: 10.1089/mdr.2021.0424] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023] Open
Abstract
Mycobacteria species include a large number of pathogenic organisms such as Mycobacterium tuberculosis, Mycobacterium leprae, and various non-tuberculous mycobacteria. Mycobacterial membrane protein large 3 (MmpL3) is an essential mycolic acid and lipid transporter required for growth and cell viability. In the last decade, numerous studies have characterized MmpL3 with respect to protein function, localization, regulation, and substrate/inhibitor interactions. This review summarizes new findings in the field and seeks to assess future areas of research in our rapidly expanding understanding of MmpL3 as a drug target. An atlas of known MmpL3 mutations that provide resistance to inhibitors is presented, which maps amino acid substitutions to specific structural domains of MmpL3. In addition, chemical features of distinct classes of Mmpl3 inhibitors are compared to provide insights into shared and unique features of varied MmpL3 inhibitors.
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Affiliation(s)
- John T Williams
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Robert B Abramovitch
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
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de Sousa-d'Auria C, Constantinesco F, Bayan N, Constant P, Tropis M, Daffé M, Graille M, Houssin C. Cg1246, a new player in mycolic acid biosynthesis in Corynebacterium glutamicum. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 35394419 DOI: 10.1099/mic.0.001171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Mycolic acids are key components of the complex cell envelope of Corynebacteriales. These fatty acids, conjugated to trehalose or to arabinogalactan form the backbone of the mycomembrane. While mycolic acids are essential to the survival of some species, such as Mycobacterium tuberculosis, their absence is not lethal for Corynebacterium glutamicum, which has been extensively used as a model to depict their biosynthesis. Mycolic acids are first synthesized on the cytoplasmic side of the inner membrane and transferred onto trehalose to give trehalose monomycolate (TMM). TMM is subsequently transported to the periplasm by dedicated transporters and used by mycoloyltransferase enzymes to synthesize all the other mycolate-containing compounds. Using a random transposition mutagenesis, we recently identified a new uncharacterized protein (Cg1246) involved in mycolic acid metabolism. Cg1246 belongs to the DUF402 protein family that contains some previously characterized nucleoside phosphatases. In this study, we performed a functional and structural characterization of Cg1246. We showed that absence of the protein led to a significant reduction in the pool of TMM in C. glutamicum, resulting in a decrease in all other mycolate-containing compounds. We found that, in vitro, Cg1246 has phosphatase activity on organic pyrophosphate substrates but is most likely not a nucleoside phosphatase. Using a computational approach, we identified important residues for phosphatase activity and constructed the corresponding variants in C. glutamicum. Surprisingly complementation with these non-functional proteins fully restored the defect in TMM of the Δcg1246 mutant strain, suggesting that in vivo, the phosphatase activity is not involved in mycolic acid biosynthesis.
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Affiliation(s)
- Célia de Sousa-d'Auria
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Florence Constantinesco
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Nicolas Bayan
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Patricia Constant
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Maryelle Tropis
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Mamadou Daffé
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Marc Graille
- Laboratoire de Biologie Structurale de la Cellule (BIOC), CNRS, Ecole polytechnique, IP Paris, F-91128 Palaiseau Cedex, Paris, France
| | - Christine Houssin
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
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