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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. 
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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. 
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Bacterial protein maturation is a tightly regulated process that ensures newly synthesized polypeptides achieve correct functional conformations. This maturation involves a series of modifications, folding events, and quality control steps, often assisted by specialized chaperone proteins.N-Terminal ModificationsThe maturation of bacterial polypeptides begins cotranslationally as the polypeptide exits the ribosome. The first amino acid, N-formylmethionine (fMet), is typically modified at the...
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Aminoglycosides constitute a highly potent class of bactericidal antibiotics that exert their antimicrobial effects by targeting the bacterial ribosome, specifically disrupting protein synthesis. These polycationic molecules consist of amino-modified sugars linked via glycosidic bonds to an aminocyclitol core such as 2-deoxystreptamine or streptamine. Their strong positive charges facilitate tight binding to the negatively charged phosphate backbone of ribosomal RNA (rRNA), primarily at the 16S...
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Updated: May 9, 2026

A11-positive &#946;-amyloid Oligomer Preparation and Assessment Using Dot Blotting Analysis
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Published on: May 22, 2018

Microcin e492 amyloid formation is retarded by posttranslational modification.

Andrés Marcoleta1, Macarena Marín, Gabriela Mercado

  • 1Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile.

Journal of Bacteriology
|July 10, 2013
PubMed
Summary

The proportion of unmodified microcin E492 directly influences its antibacterial activity and amyloid fiber formation. Higher levels of the unmodified form decrease activity and promote amyloidogenesis, impacting bacteriocin function.

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Rapid Generation of Amyloid from Native Proteins In vitro
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Rapid Generation of Amyloid from Native Proteins In vitro

Published on: December 5, 2013

Area of Science:

  • Microbiology
  • Biochemistry
  • Structural Biology

Background:

  • Microcin E492 is a channel-forming bacteriocin exported in two forms: unmodified (inactive) and C-terminally modified (active).
  • The unmodified form accumulates during stationary phase due to reduced maturation gene expression, leading to inactivation.
  • Posttranslational modification is crucial for microcin E492's antibacterial activity.

Purpose of the Study:

  • To investigate the relationship between the proportion of unmodified microcin E492 and its amyloid fiber formation.
  • To determine how changes in microcin E492 forms affect antibacterial activity and amyloidogenesis.
  • To elucidate the role of the unmodified form in enhancing amyloid fiber formation.

Main Methods:

  • Construction of bacterial strains with altered proportions of unmodified and modified microcin E492.
  • Analysis of antibacterial activity across different growth phases.
  • Assessment of amyloid fiber formation kinetics and morphology.
  • Comparative studies using exclusively unmodified or modified forms for amyloid seeding.

Main Results:

  • Increased expression of maturation genes enhanced antibacterial activity and reduced amyloid fiber formation.
  • Higher expression of microcin E492 protein led to decreased modified form levels, reduced activity, and increased amyloid fiber formation.
  • Unmodified microcin E492 demonstrated more efficient amyloid nucleation and incorporation into fibers compared to the modified form.
  • Amyloid fiber morphology remained consistent regardless of the form's proportion.

Conclusions:

  • The proportion of unmodified microcin E492 is a critical determinant of its antibacterial efficacy and propensity for amyloid formation.
  • Unmodified microcin E492 significantly promotes amyloidogenesis, negatively impacting its antimicrobial function.
  • The nucleation and incorporation kinetics favor the unmodified form in amyloid fiber assembly.