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Pull-down of Calmodulin-binding Proteins
07:51

Pull-down of Calmodulin-binding Proteins

Published on: January 23, 2012

Selective degradation of oxidized calmodulin by the 20 S proteasome

D A Ferrington1, H Sun, K K Murray

  • 1Department of Ophthalmology, University of Minnesota, Minneapolis, Minnesota 55455, USA.

The Journal of Biological Chemistry
|September 30, 2000
PubMed

Insights

Oxidized calmodulin undergoes enhanced degradation by the proteasome. Decreased secondary structure, not surface hydrophobicity, drives this selective protein breakdown.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Proteostasis

Background:

  • Calmodulin is a crucial calcium-binding protein.
  • Oxidative stress can modify proteins, affecting their function and stability.
  • The proteasome is the cell's primary machinery for protein degradation.

Purpose of the Study:

  • To elucidate the mechanisms targeting oxidized calmodulin for proteasomal degradation.
  • To identify the structural changes in calmodulin that trigger its degradation.
  • To understand the role of methionine oxidation in calmodulin's proteolytic susceptibility.

Main Methods:

  • Mass spectrometry to analyze proteolytic fragments.
  • Circular dichroism and fluorescence spectroscopy to assess structural changes.
  • Investigating the effects of calcium binding and methionine sulfoxide reductase on degradation rates.

Main Results:

  • Methionine oxidation significantly enhances calmodulin degradation by the 20 S proteasome.
  • Degradation proceeds via large fragments followed by smaller peptides (6-12 amino acids).
  • A strong correlation exists between reduced secondary structure and increased degradation rate.
  • Calcium binding or repair by methionine sulfoxide reductase mimics these degradation-enhancing structural changes.
  • Altered surface hydrophobicity does not affect degradation rates, suggesting it's not the primary trigger.

Conclusions:

  • Decreased secondary structure in oxidized calmodulin exposes sites for proteasomal cleavage.
  • Proteasome degrades oxidized calmodulin in a nonprocessive manner.
  • Structural destabilization, rather than hydrophobicity, is key to selective oxidized calmodulin degradation.

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