Functional amyloid in Pseudomonas |
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Authors: | Morten S Dueholm Steen V Petersen Mads Sønderkær Poul Larsen Gunna Christiansen Kim L Hein Jan J Enghild Jeppe L Nielsen Kåre L Nielsen Per H Nielsen Daniel E Otzen |
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Institution: | 1. Centre for Insoluble Protein Structures, Interdisciplinary Nanoscience Center (iNANO), Department of Molecular Biology, University of Aarhus (iNANO), 8000 Aarhus C, Denmark;2. Department of Biotechnology, Chemistry, and Environmental Engineering, Aalborg University, 9000 Aalborg, Denmark;3. Departments of Medical Biochemistry;4. Medical Microbiology;5. Molecular Biology, University of Aarhus (iNANO), 8000 Aarhus C, Denmark. |
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Abstract: | Amyloids are highly abundant in many microbial biofilms and may play an important role in their architecture. Nevertheless, little is known of the amyloid proteins. We report the discovery of a novel functional amyloid expressed by a Pseudomonas strain of the P. fluorescens group. The amyloid protein was purified and the amyloid‐like structure verified. Partial sequencing by MS/MS combined with full genomic sequencing of the Pseudomonas strain identified the gene coding for the major subunit of the amyloid fibril, termed fapC. FapC contains a thrice repeated motif that differs from those previously found in curli fimbrins and prion proteins. The lack of aromatic residues in the repeat shows that aromatic side chains are not needed for efficient amyloid formation. In contrast, glutamine and asparagine residues seem to play a major role in amyloid formation as these are highly conserved in curli, prion proteins and FapC. fapC is conserved in many Pseudomonas strains including the opportunistic pathogen P. aeruginosa and is situated in a conserved operon containing six genes, of which one encodes a fapC homologue. Heterologous expression of the fapA–F operon in Escherichia coli BL21(DE3) resulted in a highly aggregative phenotype, showing that the operon is involved in biofilm formation. |
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