title: The Tubular Sheaths Encasing Methanosaeta thermophila Filaments Are Functional Amyloids.
abstract: Archaea are renowned for their ability to thrive in extreme environments, although they can be found in virtually all habitats. Their adaptive success is linked to their unique cell envelopes that are extremely resistant to chemical and thermal denaturation and that resist proteolysis by common proteases. Here we employ amyloid-specific conformation antibodies and biophysical techniques to show that the extracellular cell wall sheaths encasing the methanogenic archaea Methanosaeta thermophila PT are functional amyloids. Depolymerization of sheaths and subsequent MS/MS analyses revealed that the sheaths are composed of a single major sheath protein (MspA). The amyloidogenic nature of MspA was confirmed by in vitro amyloid formation of recombinant MspA under a wide range of environmental conditions. This is the first report of a functional amyloid from the archaeal domain of life. The amyloid nature explains the extreme resistance of the sheath, the elastic properties that allow diffusible substrates to penetrate through expandable hoop boundaries, and how the sheaths are able to split and elongate outside the cell. The archaeal sheath amyloids do not share homology with any of the currently known functional amyloids and clearly represent a new function of the amyloid protein fold.
authors.affiliation: From the Center for Microbial Communities, Department of Chemistry and Biosciences, Aalborg University, 9220 Aalborg, Denmark.
authors.forename: Morten S
authors.identifier: http://orcid.org/0000-0003-4135-2670
authors.initials: MS
authors.lastname: Dueholm
authors.affiliation: From the Center for Microbial Communities, Department of Chemistry and Biosciences, Aalborg University, 9220 Aalborg, Denmark.
authors.forename: Poul
authors.initials: P
authors.lastname: Larsen
authors.affiliation: the Department of Biosciences.
authors.forename: Kai
authors.initials: K
authors.lastname: Finster
authors.affiliation: the Interdisciplinary Nanoscience Center (iNANO) and Center for Insoluble Protein Structures (inSPIN), the Department of Molecular Biology and Genetics, and.
authors.forename: Marcel R
authors.initials: MR
authors.lastname: Stenvang
authors.affiliation: the Department of Biomedicine, Aarhus University, 8000 Aarhus, Denmark.
authors.forename: Gunna
authors.initials: G
authors.lastname: Christiansen
authors.affiliation: the Interdisciplinary Nanoscience Center (iNANO) and Center for Insoluble Protein Structures (inSPIN), the Department of Molecular Biology and Genetics, and.
authors.forename: Brian S
authors.initials: BS
authors.lastname: Vad
authors.affiliation: the Department of Molecular Biology and Genetics, and.
authors.forename: Andreas
authors.initials: A
authors.lastname: Bøggild
authors.affiliation: the Interdisciplinary Nanoscience Center (iNANO) and Center for Insoluble Protein Structures (inSPIN), the Department of Molecular Biology and Genetics, and.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Otzen
authors.affiliation: From the Center for Microbial Communities, Department of Chemistry and Biosciences, Aalborg University, 9220 Aalborg, Denmark, phn@bio.aau.dk.
authors.forename: Per Halkjær
authors.initials: PH
authors.lastname: Nielsen
mesh_terms: D000682:Amyloid / Q000096:biosynthesis / Q000502:physiology*; D019640:Methanosarcinales / Q000378:metabolism / Q000502:physiology*; D046529:Microscopy, Electron, Transmission; D053719:Tandem Mass Spectrometry
chemical_list: D000682:Amyloid
keywords: amyloid; archaea; cell wall; functional amyloid; methanogen; protein folding; sheath; structure-function