1
|
Buchinger E, Knudsen DH, Behrens MA, Pedersen JS, Aarstad OA, Tøndervik A, Valla S, Skjåk-Bræk G, Wimmer R, Aachmann FL. Structural and functional characterization of the R-modules in alginate C-5 epimerases AlgE4 and AlgE6 from Azotobacter vinelandii. J Biol Chem 2014; 289:31382-96. [PMID: 25266718 DOI: 10.1074/jbc.m114.567008] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The bacterium Azotobacter vinelandii produces a family of seven secreted and calcium-dependent mannuronan C-5 epimerases (AlgE1-7). These epimerases are responsible for the epimerization of β-D-mannuronic acid (M) to α-L-guluronic acid (G) in alginate polymers. The epimerases display a modular structure composed of one or two catalytic A-modules and from one to seven R-modules having an activating effect on the A-module. In this study, we have determined the NMR structure of the three individual R-modules from AlgE6 (AR1R2R3) and the overall structure of both AlgE4 (AR) and AlgE6 using small angle x-ray scattering. Furthermore, the alginate binding ability of the R-modules of AlgE4 and AlgE6 has been studied with NMR and isothermal titration calorimetry. The AlgE6 R-modules fold into an elongated parallel β-roll with a shallow, positively charged groove across the module. Small angle x-ray scattering analyses of AlgE4 and AlgE6 show an overall elongated shape with some degree of flexibility between the modules for both enzymes. Titration of the R-modules with defined alginate oligomers shows strong interaction between AlgE4R and both oligo-M and MG, whereas no interaction was detected between these oligomers and the individual R-modules from AlgE6. A combination of all three R-modules from AlgE6 shows weak interaction with long M-oligomers. Exchanging the R-modules between AlgE4 and AlgE6 resulted in a novel epimerase called AlgE64 with increased G-block forming ability compared with AlgE6.
Collapse
Affiliation(s)
- Edith Buchinger
- From the Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Frederik Bajers vej 7H, DK-9220 Aalborg, Denmark, the Department of Biotechnology, Norwegian Biopolymer Laboratory (NOBIPOL), Norwegian University of Science and Technology, Sem Sælands vei 6/8, 7491 Trondheim, Norway
| | - Daniel H Knudsen
- From the Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Frederik Bajers vej 7H, DK-9220 Aalborg, Denmark
| | - Manja A Behrens
- the Interdisciplinary Nanoscience Center and Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, DK-8000, Denmark, and
| | - Jan Skov Pedersen
- the Interdisciplinary Nanoscience Center and Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, DK-8000, Denmark, and
| | - Olav A Aarstad
- the Department of Biotechnology, Norwegian Biopolymer Laboratory (NOBIPOL), Norwegian University of Science and Technology, Sem Sælands vei 6/8, 7491 Trondheim, Norway
| | - Anne Tøndervik
- the Department of Bioprocess Technology, SINTEF Materials and Chemistry, N-7465 Trondheim, Norway
| | - Svein Valla
- the Interdisciplinary Nanoscience Center and Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, DK-8000, Denmark, and
| | - Gudmund Skjåk-Bræk
- the Department of Biotechnology, Norwegian Biopolymer Laboratory (NOBIPOL), Norwegian University of Science and Technology, Sem Sælands vei 6/8, 7491 Trondheim, Norway
| | - Reinhard Wimmer
- From the Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Frederik Bajers vej 7H, DK-9220 Aalborg, Denmark
| | - Finn L Aachmann
- the Department of Biotechnology, Norwegian Biopolymer Laboratory (NOBIPOL), Norwegian University of Science and Technology, Sem Sælands vei 6/8, 7491 Trondheim, Norway,
| |
Collapse
|
2
|
Oeemig JS, Lynggaard C, Knudsen DH, Hansen FT, Nørgaard KD, Schneider T, Vad BS, Sandvang DH, Nielsen LA, Neve S, Kristensen HH, Sahl HG, Otzen DE, Wimmer R. Eurocin, a new fungal defensin: structure, lipid binding, and its mode of action. J Biol Chem 2012; 287:42361-72. [PMID: 23093408 DOI: 10.1074/jbc.m112.382028] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Antimicrobial peptides are a new class of antibiotics that are promising for pharmaceutical applications because they have retained efficacy throughout evolution. One class of antimicrobial peptides are the defensins, which have been found in different species. Here we describe a new fungal defensin, eurocin. Eurocin acts against a range of Gram-positive human pathogens but not against Gram-negative bacteria. Eurocin consists of 42 amino acids, forming a cysteine-stabilized α/β-fold. The thermal denaturation data point shows the disulfide bridges being responsible for the stability of the fold. Eurocin does not form pores in cell membranes at physiologically relevant concentrations; it does, however, lead to limited leakage of a fluorophore from small unilamellar vesicles. Eurocin interacts with detergent micelles, and it inhibits the synthesis of cell walls by binding equimolarly to the cell wall precursor lipid II.
Collapse
Affiliation(s)
- Jesper S Oeemig
- Department of Biotechnology, Chemistry, and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|