The Sheaths of Methanospirillum Are Made of a New Type of Amyloid Protein

Line Friis Bakmann Christensen, Lonnie Maria Hansen, Kai Finster, Gunna Christiansen, Per Halkjaer Nielsen, Daniel Erik Otzen, Morten Simonsen Dueholm*

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

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Abstract

The genera Methanospirillum and Methanosaeta contain species of anaerobic archaea that grow and divide within proteinaceous tubular sheaths that protect them from environmental stressors. The sheaths of Methanosaeta thermophila PT are composed of the 60.9 kDa major sheath protein MspA. In this study we show that sheaths purified from Methanospirillum hungatei JF-1 are regularly striated tubular structures with amyloid-like properties similar to those of M. thermophila PT. Depolymerizing the sheaths from M. hungatei JF-1 allowed us to identify a 40.6 kDa protein (WP_011449234.1) that shares 23% sequence similarity to MspA from M. thermophila PT (ABK14853.1), indicating that they might be distant homologs. The genome of M. hungatei JF-1 encodes six homologs of the identified MspA protein. Several homologs also exist in the related strains Methanospirillum stamsii Pt1 (7 homologs, 28-66% sequence identity), M. lacunae Ki8-1 C (15 homologs, 29-60% sequence identity) and Methanolinea tarda NOBI-1 (2 homologs, 31% sequence identity). The MspA protein discovered here could accordingly represent a more widely found sheath protein than the MspA from M. thermophila PT, which currently has no homologs in the NCBI Reference Sequence database (RefSeq).

Original languageEnglish
Article number2729
JournalFrontiers in Microbiology
Volume9
IssueNOV
Number of pages11
ISSN1664-302X
DOIs
Publication statusPublished - 2018

Keywords

  • ABUNDANCE
  • ADHESINS
  • BIOGENESIS
  • CONFORMATION
  • EPITOPE
  • HUNGATEI GP1
  • METHANOGENIC BACTERIA
  • METHANOTHRIX-CONCILII
  • PEPTIDES
  • PSEUDOMONAS
  • archaea
  • functional amyloid
  • homologs
  • methanogen
  • sheath protein

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