Related Experiment Video

Updated: May 9, 2026

A11-positive β-amyloid Oligomer Preparation and Assessment Using Dot Blotting Analysis
06:17

A11-positive β-amyloid Oligomer Preparation and Assessment Using Dot Blotting Analysis

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

Insights

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.

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.

More Related Videos

Modified Roller Tube Method for Precisely Localized and Repetitive Intermittent Imaging During Long-term Culture of Brain Slices in an Enclosed System09:52

Modified Roller Tube Method for Precisely Localized and Repetitive Intermittent Imaging During Long-term Culture of Brain Slices in an Enclosed System

Published on: December 28, 2017

Rapid Generation of Amyloid from Native Proteins In vitro05:48

Rapid Generation of Amyloid from Native Proteins In vitro

Published on: December 5, 2013

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...
Bacterial Protein Maturation01:26

Bacterial Protein Maturation

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...
Inhibitors of Bacterial Protein Synthesis01:25

Inhibitors of Bacterial Protein Synthesis

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...
Protein Modifications in the RER01:26

Protein Modifications in the RER

Modification of secretory and transmembrane proteins entering the rough ER begins in the ER lumen. These modifications aid in protein folding and stabilize the acquired tertiary structure. Protein modifications in the rough ER co-occur at different stages of protein folding.
Broadly, these modifications can be categorized into four main categories — glycosylation, formation of disulfide bonds, assembly of protein subunits, and specific proteolytic cleavages like removal of signal sequences.