Nucleator-dependent intercellular assembly of adhesive curli organelles in Escherichia coli.

Hammar, Mårten; Zhao, Bin; Normark, Staffan

doi:10.1073/pnas.93.13.6562

Cited by 281 publications

(320 citation statements)

References 28 publications

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“…CsgA molecules secreted by csgB donor cells polymerize into amyloid fibers on the csgA acceptor cells, as shown in Figure 5 (b). 6 We performed an interbacterial complementation assay to test CsgB-mediated heteronucleation responsiveness of CsgA, CsgA Q49A and CsgA N144A in vivo. CsgA secreted from csgBA/pLR5 (donor) responded to the heteronucleation of CsgB on the csgA cells (acceptor), and formed an amyloid fiber on the surface of csgA cells as demonstrated by Congo red ( Figure 5(b)).…”

Section: Ala Scan Mutagenesis Of the Aromatic Residuesmentioning

confidence: 99%

“…5 In E. coli, the polymerization of the major curli fiber subunit protein CsgA into an amyloid fiber is dependent on the minor curli subunit protein, CsgB. 6 CsgA remains soluble until it encounters outer membrane-localized CsgB. 5 CsgB has also been demonstrated to have amyloid-forming properties and apparently serves as a template for CsgA polymerization.…”

Section: Introductionmentioning

confidence: 99%

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Sequence Determinants of Bacterial Amyloid Formation

Wang

Chapman

2008

Journal of Molecular Biology

108

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SummaryAmyloids are proteinaceous fibers commonly associated with neurodegenerative diseases and prionbased encephalopathies. Many different polypeptides can form amyloid fibers, leading to the suggestion that amyloid is a primitive main-chain-dominated structure. A growing body of evidence suggests that amino acid side chains dramatically influence amyloid formation. The specific role fulfilled by side chains in amyloid formation, especially in vivo, remains poorly understood. Here, we determined the role of internally conserved polar and aromatic residues in promoting amyloidogenesis of the functional amyloid protein, CsgA. CsgA is the major protein component of curli fibers assembled by enteric bacteria such as Escherichia coli and Salmonella spp. In vivo CsgA polymerization into an amyloid fiber requires the CsgB nucleator protein. The CsgA amyloid core region is composed of five repeating units, defined by regularly spaced Ser, Gln and Asn residues. The results of a comprehensive alanine scan mutagenesis screen showed that Gln and Asn residues at positions 49, 54, 139 and 144 were critical for curli assembly. Alanine substitution of Q49 or N144 impeded the ability of CsgA to respond to CsgB-mediated heteronucleation, and the ability of CsgA to self-polymerize in vitro. However, CsgA proteins harboring these mutations were still seeded by preformed wild-type CsgA fibers in vitro. This suggests that CsgA-fibril-mediated seeding and CsgBmediated heteronucleation have distinguishable mechanisms. Remarkably, Gln residues at positions 49 and 139 could not be replaced by Asn residues without interfering with curli assembly, suggesting that the side chain requirements were especially stringent at these positions. This analysis demonstrates that bacterial amyloid formation is driven by specific side chain contacts and provides a clear illustration of the essential roles of specific side chains in promoting amyloid formation.

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Section: Ala Scan Mutagenesis Of the Aromatic Residuesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Sequence Determinants of Bacterial Amyloid Formation

Wang

Chapman

2008

Journal of Molecular Biology

108

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“…Anchored Fapl may function as a cellbound nucleator protein to initiate fimbrial assembly, as has been described for polymerization of E. coli curlin during curli fimbriae assembly (Hammar et al, 1996). In fact, S, parasacnguis fimbriae are morphologically similar to E. coli curli.…”

Section: Oto 1998) Andmentioning

confidence: 86%

“…Curli are highly stable and are not solubilized in hot denaturing reagents. Harsh treatment (90% formic acid) is required to depolymerize curli into soluble subunits (Hammar et al, 1996).…”

Section: )111540lmentioning

confidence: 99%

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Molecular Strategies for Fimbrial Expression and Assembly

Fives-Taylor

2001

Critical Reviews in Oral Biology & Medicine

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Fimbriae or pili are long, filamentous, multimeric macromolecules found on the bacterial cell surface. Bacteria express a diverse array of fimbriae or pili that are involved in bacterial adherence and invasion. Fimbriae can be categorized based on their modes of expression and assembly. Type 1 fimbriae and P pili are distributed peritrichously and translocated to the cell surface by a chaperone/usher pathway. Type 4 pili are located at the pole of the cell and assembled via the type 11 secretion system. Curli fimbriae are coiled surface structures assembled by an extracellular nucleation/precipitation pathway. Fimbriae of oral Gram-negative and Gram-positive bacteria have not been well-studied as compared with the fimbriae of enteric pathogens. Oral pathogens, such as Eikenella corrodens, Actinobacillus actinomycetemcomitans, and Porphyromonas gingivalis, possess fimbriae that have been implicated in bacterial adhesion and invasion. These fimbriae are potential virulence factors in oral infectious processes. A. actinomycetemcomitans and E. corrodens have Type 4-like fimbriae, whereas P. gingivalis displays a unique type of fimbriae. To date, fimbriae of the oral primary colonizers, Actinomyces naeslundii and Streptococcus parasanguis, represent the only fimbriae characterized for any Gram-positive bacteria. The putative major fimbrial subunits, FimA and FimP of A. naeslundii and FapI of S. parasanguis, contain a signal sequence and cell-wall-sorting signal. The presence of extensive dipeptide repeats in FapI makes it unique among fimbrial molecules. Based on experimental data, a nucleation/precipitation pathway is proposed for fimbrial biogenesis of both S. parasanguis and A. naeslundii, although we cannot rule out an alternative covalent linkage model. The model systems described in this review served as a framework for hypotheses for how the known molecular factors of fimbriae on oral bacteria may be expressed and assembled.

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Structural and functional characterization of the Curli adaptor protein CsgF

et al. 2018

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Curli are functional amyloids that form a major part of the biofilm produced by many enterobacteriaceae. A multiprotein system around the outer membrane protein CsgG is in charge of the export and controlled propagation of the main Curli subunits, CsgA and CsgB. CsgF is essential for the linkage of the main amyloid-forming proteins to the cell surface. Here, we present a profound biochemical and biophysical characterization of recombinant CsgF, highlighted by a solution NMR structure of CsgF in the presence of dihexanoylphosphocholine micelles. Interestingly, CsgF contains large unstructured domains and does not show a globular fold. The data presented shed new light on the molecular mechanism of Curli amyloid surface attachment.

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Nucleator-dependent intercellular assembly of adhesive curli organelles in Escherichia coli.

Cited by 281 publications

References 28 publications

Sequence Determinants of Bacterial Amyloid Formation

Sequence Determinants of Bacterial Amyloid Formation

Molecular Strategies for Fimbrial Expression and Assembly

Structural and functional characterization of the Curli adaptor protein CsgF

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