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Related Concept Videos

Amyloid Fibrils03:03

Amyloid Fibrils

Amyloid fibrils are aggregates of misfolded proteins.  Under most circumstances, misfolded proteins are either refolded by chaperone proteins or degraded by the proteasome. However, in the case of a mutation or a disease, these proteins can accumulate to form large clusters and often further assemble to form elongated fibers, called fibrils. 
Amyloid deposits were observed as early as 1639 in the liver and the spleen.   In 1854, Rudolph Virchow performed iodine staining, normally used to...
Amyloid Fibrils03:03

Amyloid Fibrils

Amyloid fibrils are aggregates of misfolded proteins.  Under most circumstances, misfolded proteins are either refolded by chaperone proteins or degraded by the proteasome. However, in the case of a mutation or a disease, these proteins can accumulate to form large clusters and often further assemble to form elongated fibers, called fibrils. 
Amyloid deposits were observed as early as 1639 in the liver and the spleen.   In 1854, Rudolph Virchow performed iodine staining, normally used to...
Determinants of Bacterial Pathogenicity and Virulence01:20

Determinants of Bacterial Pathogenicity and Virulence

Pathogenic bacteria employ a variety of strategies to establish infections, including the secretion of extracellular enzymes that act as potent virulence factors. These enzymes facilitate bacterial colonization of host tissues and help evade immune surveillance. By targeting structural components of host tissues and interfering with immune mechanisms, these enzymes play a pivotal role in disease progression.Extracellular Enzymes Facilitating Tissue Invasion: Several bacterial pathogens secrete...
Formation of Lipopolysaccharides01:19

Formation of Lipopolysaccharides

Lipopolysaccharides (LPS) are crucial components of the outer membrane of Gram-negative bacteria, serving both structural and functional roles. It contributes to membrane stability and protects bacteria from host immune responses. LPS is composed of three major regions—lipid A, a core oligosaccharide, and an O antigen. The biosynthesis and assembly of LPS involve a highly coordinated set of enzymatic reactions and transport mechanisms. Additionally, LPS is recognized as an endotoxin, triggering...
Translation01:31

Translation

Lesson: Translation
Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes the final step in the expression of genes. This process is carried out by ribosomes, complexes of protein and specialized RNA molecules. Ribosomes, transfer RNA (tRNA), and other proteins produce a chain of amino acids—the polypeptide—as the end product of translation.
Translation Produces the Building Blocks of Life
Translation01:31

Translation

Lesson: Translation
Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes the final step in the expression of genes. This process is carried out by ribosomes, complexes of protein and specialized RNA molecules. Ribosomes, transfer RNA (tRNA), and other proteins produce a chain of amino acids—the polypeptide—as the end product of translation.
Translation Produces the Building Blocks of Life

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Updated: Jul 4, 2026

Rapid Generation of Amyloid from Native Proteins In vitro
05:48

Rapid Generation of Amyloid from Native Proteins In vitro

Published on: December 5, 2013

Sequence determinants of bacterial amyloid formation.

Xuan Wang1, Matthew R Chapman

  • 1Department of Molecular, Cellular and Developmental Biology, University of Michigan, 830 N. University, Ann Arbor, MI 48109, USA.

Journal of Molecular Biology
|June 21, 2008
PubMed
Summary

Bacterial amyloid formation, like curli assembly, depends on specific amino acid side chains. Key glutamine and asparagine residues in CsgA are essential for proper fiber assembly and nucleation.

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Rapid Generation of Amyloid from Native Proteins In vitro
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Methods for Detecting Cytotoxic Amyloids Following Infection of Pulmonary Endothelial Cells by Pseudomonas aeruginosa
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Methods for Detecting Cytotoxic Amyloids Following Infection of Pulmonary Endothelial Cells by Pseudomonas aeruginosa

Published on: July 12, 2018

Area of Science:

  • Microbiology
  • Biochemistry
  • Structural Biology

Background:

  • Amyloids are protein aggregates linked to diseases and primitive structures.
  • Amino acid side chains are known to influence amyloid formation, but their specific roles are unclear.
  • Curli fibers, functional amyloids in bacteria like E. coli, are crucial for biofilm formation.

Purpose of the Study:

  • To investigate the role of specific amino acid side chains in the in vivo amyloidogenesis of the curli fiber protein CsgA.
  • To determine how conserved polar and aromatic residues in CsgA impact polymerization and nucleation processes.
  • To differentiate the mechanisms of CsgB-mediated heteronucleation and CsgA-fibril-mediated seeding.

Main Methods:

  • Comprehensive alanine scan mutagenesis of the CsgA protein.
  • In vitro polymerization and seeding assays.
  • In vivo curli assembly analysis in enteric bacteria.

Main Results:

  • Glutamine (Gln) and asparagine (Asn) residues at positions 49, 54, 139, and 144 were critical for curli assembly.
  • Mutations at Q49 and N144 impaired CsgB-mediated heteronucleation and CsgA self-polymerization.
  • While CsgA mutants could be seeded by pre-formed fibers, specific Gln residues could not be substituted by Asn, indicating stringent side chain requirements.

Conclusions:

  • Bacterial amyloid formation, exemplified by curli, is driven by specific amino acid side chain interactions.
  • Conserved polar residues, particularly Gln and Asn, play essential and distinct roles in CsgA amyloidogenesis.
  • Distinct mechanisms govern CsgB-mediated nucleation and fibril-mediated seeding in CsgA polymerization.