Related Experiment Video

Updated: May 10, 2026

Nuclear Magnetic Resonance Spectroscopy for the Identification of Multiple Phosphorylations of Intrinsically Disordered Proteins
12:47

Nuclear Magnetic Resonance Spectroscopy for the Identification of Multiple Phosphorylations of Intrinsically Disordered Proteins

Published on: December 27, 2016

Measurement of active site ionization equilibria in the 670 kDa proteasome core particle using methyl-TROSY NMR

Algirdas Velyvis1, Lewis E Kay

  • 1Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada M5S 1A8. avelyvis@pound.med.utoronto.ca

Journal of the American Chemical Society
|June 27, 2013
PubMed

Insights

The 20S proteasome

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Structural Biology

Background:

  • The 20S proteasome core particle regulates cellular function via proteolysis.
  • It is a key drug target for cancer therapies.
  • Understanding substrate cleavage mechanisms is crucial for pharmaceutical development.

Purpose of the Study:

  • To elucidate the role of Thr1 in the 20S proteasome's catalytic mechanism.
  • To identify the base responsible for accepting the Thr1 proton during peptide bond cleavage.

Main Methods:

  • Utilized a highly deuterated 20S proteasome sample.
  • Incorporated (13)CH3 labeling at Thr-gamma positions.
  • Measured the pKa of the Thr1 amino group.

Main Results:

  • The pKa of the Thr1 amino group was determined to be 6.3.
  • This indicates the Thr1 amino group is deprotonated during maximal enzyme activity.
  • Provides evidence for the Thr1 amino group acting as the catalytic base.

Conclusions:

  • The terminal amino group of Thr1 acts as the base in the initial step of peptide bond cleavage by the 20S proteasome.
  • This finding clarifies a key aspect of proteasome catalytic mechanism.
  • Informs the design of novel proteasome-targeting drugs.

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