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N-Terminal methylation of proteasome subunit Rpt1 in yeast

Yayoi Kimura1, Yoichi Kurata, Akiyo Ishikawa

  • 1Graduate School of Medical Life Science and Advanced Medical Research Center, Yokohama City University, Yokohama, Japan.

Proteomics
|September 17, 2013
PubMed

Insights

N-terminal methylation of yeast Rpt1, a 26S proteasome subunit, affects cell growth and stress tolerance. This modification, involving the Pro-Lys sequence, is not conserved across species.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • The 26S proteasome degrades ubiquitinated proteins, crucial for cellular regulation.
  • Regulatory particles, including ATPase (Rpt) subunits, facilitate substrate unfolding and translocation into the 20S proteasome core.
  • N-terminal modifications can influence protein function and stability.

Purpose of the Study:

  • To investigate N-terminal modifications of the yeast Rpt1 subunit.
  • To explore the functional significance of the Pro-Lys (PK) sequence in Rpt1.
  • To determine the evolutionary conservation of Rpt1 N-methylation.

Main Methods:

  • Mass spectrometry (MS) was employed to analyze N-terminal modifications of yeast Rpt1.
  • Mutant yeast strains lacking the PK sequence in Rpt1 were generated.
  • Cell growth and stress sensitivity assays were performed on mutant strains.

Main Results:

  • Yeast Rpt1's N-terminal Pro residue can be unmodified, mono-methylated, or di-methylated after initiation methionine removal.
  • N-methylation of Rpt1 was found to be evolutionarily non-conserved.
  • Deletion of the PK sequence abolished N-methylation, impaired cell growth, and increased stress sensitivity.

Conclusions:

  • N-methylation of the Rpt1 subunit, potentially via its PK sequence, plays a role in yeast cell growth.
  • This N-methylation may also contribute to stress tolerance in yeast.
  • The findings highlight a specific post-translational modification impacting proteasome function and cellular fitness.
Keywords:
Cell biologyMSN-MethylationProteasome

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