Identification of a protein kinase which phosphorylate α4 subunit of the 26S proteasome in goldfish oocytes

R. Horiguchi, M. Yoshikuni, M. Tokumoto, Y. Nagahama, T. Tokumoto

Research output: Contribution to journalArticle


To investigate the regulatory mechanism for the proteasome in the meiotic cell cycle, we purified the 26S proteasome from immature (in G2-phase) and mature (in M-phase) oocytes, and compared its subunits by immunoblotting. A monoclonal antibody, GC3β (anti-goldfish 20S proteasome component 3β) cross-reacted with two bands in the 26S proteasome from immature oocytes, however the upper band was absent in the 26S proteasome from mature oocytes. cDNAs which encode the α4 subunit of goldfish 20S proteasome (α4_ca) were isolated by an immuno-screening method using GC3β. Phosphatase treatment of the 26S proteasome revealed that a part of α4_ca phosphorylated in G2-phase and dephosphorylated in M-phase. By the assay using recombinant α4_ca as a substrate, a kinase was purified by column chromatographs. Amino acid sequence analysis was performed for resulting partial purified fraction. A protein band, which well corresponded to the kinase activity, was identified as Casein kinase-1α (CK-1α). The result suggests that CK-1α phosphorylate α4 subunit of the 26S proteasome in immature oocyte of goldfish.

Original languageEnglish
Pages (from-to)255-256
Number of pages2
JournalFish Physiology and Biochemistry
Issue number3
Publication statusPublished - Dec 1 2003
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Physiology
  • Aquatic Science

Cite this