MPF from starfish oocytes at first meiotic metaphase is a heterodimer containing one molecule of cdc2 and one

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J C Labbé1, J P Capony, D Caput

  • 1CNRS and INSERM, BP 5051, Montpellier, France.

The EMBO Journal
|October 1, 1989
PubMed

Insights

Researchers purified the M-phase-specific protein kinase, also known as maturation-promoting factor (MPF), from starfish oocytes. This kinase is a heterodimer of cdc2 and cyclin B, crucial for cell cycle progression into M-phase.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Maturation-promoting factor (MPF) regulates entry into M-phase in eukaryotic cells.
  • MPF is a complex involving cdc2 and cyclin proteins.
  • Understanding MPF composition is key to cell cycle control.

Purpose of the Study:

  • To purify and characterize the M-phase-specific protein kinase (MPF) from starfish oocytes.
  • To identify the protein components of starfish MPF.
  • To elucidate the structure of MPF.

Main Methods:

  • Affinity chromatography using immobilized yeast protein suc1 for purification.
  • Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for molecular weight estimation.
  • cDNA cloning and sequencing to determine cyclin B structure.
  • Partial protein microsequencing for component identification.

Main Results:

  • Purified M-phase-specific protein kinase to near homogeneity.
  • Identified MPF as a complex of cdc2 (34-kd) and starfish cyclin (47-kd).
  • Determined the sequence of starfish cyclin B cDNA, predicting a 43,729-dalton protein.
  • Confirmed the 47-kd polypeptide is starfish cyclin via microsequencing.
  • Established MPF as a heterodimer of cdc2 and cyclin B (<100-kd).

Conclusions:

  • Starfish MPF is a heterodimer composed of cdc2 and cyclin B.
  • This composition is conserved in the regulation of eukaryotic cell cycle entry into M-phase.
  • The purified kinase is identical to the MPF that drives M-phase entry.

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