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Sun L, Vella P, Schnell R, Polyakova A, Bourenkov G, Li F, Cimdins A, Schneider TR, Lindqvist Y, Galperin MY, Schneider G, Römling U. Structural and Functional Characterization of the BcsG Subunit of the Cellulose Synthase in Salmonella typhimurium. J Mol Biol 2018; 430:3170-3189. [PMID: 30017920 DOI: 10.1016/j.jmb.2018.07.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 07/02/2018] [Accepted: 07/05/2018] [Indexed: 11/17/2022]
Abstract
Many bacteria secrete cellulose, which forms the structural basis for bacterial multicellular aggregates, termed biofilms. The cellulose synthase complex of Salmonella typhimurium consists of the catalytic subunits BcsA and BcsB and several auxiliary subunits that are encoded by two divergently transcribed operons, bcsRQABZC and bcsEFG. Expression of the bcsEFG operon is required for full-scale cellulose production, but the functions of its products are not fully understood. This work aimed to characterize the BcsG subunit of the cellulose synthase, which consists of an N-terminal transmembrane fragment and a C-terminal domain in the periplasm. Deletion of the bcsG gene substantially decreased the total amount of BcsA and cellulose production. BcsA levels were partially restored by the expression of the transmembrane segment, whereas restoration of cellulose production required the presence of the C-terminal periplasmic domain and its characteristic metal-binding residues. The high-resolution crystal structure of the periplasmic domain characterized BcsG as a member of the alkaline phosphatase/sulfatase superfamily of metalloenzymes, containing a conserved Zn2+-binding site. Sequence and structural comparisons showed that BcsG belongs to a specific family within alkaline phosphatase-like enzymes, which includes bacterial Zn2+-dependent lipopolysaccharide phosphoethanolamine transferases such as MCR-1 (colistin resistance protein), EptA, and EptC and the Mn2+-dependent lipoteichoic acid synthase (phosphoglycerol transferase) LtaS. These enzymes use the phospholipids phosphatidylethanolamine and phosphatidylglycerol, respectively, as substrates. These data are consistent with the recently discovered phosphoethanolamine modification of cellulose by BcsG and show that its membrane-bound and periplasmic parts play distinct roles in the assembly of the functional cellulose synthase and cellulose production.
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Affiliation(s)
- Lei Sun
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Peter Vella
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Robert Schnell
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Anna Polyakova
- European Molecular Biology Laboratory, Hamburg Unit, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Gleb Bourenkov
- European Molecular Biology Laboratory, Hamburg Unit, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Fengyang Li
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Annika Cimdins
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Thomas R Schneider
- European Molecular Biology Laboratory, Hamburg Unit, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Ylva Lindqvist
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Michael Y Galperin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA.
| | - Gunter Schneider
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden.
| | - Ute Römling
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, S-171 77 Stockholm, Sweden.
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