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Methionine aminopeptidase II: A molecular chaperone for sarcoplasmic reticulum calcium ATPase

Shunsuke Noguchi1, Tohru Komiya, Hiroshi Eguchi

  • 1Department of Bioscience and Bioinformatics, Kyushu Institute of Technology, Iizuka 820-8502, Japan.

The Journal of Membrane Biology
|April 7, 2007
PubMed

Insights

Methionine aminopeptidase II (MetAP2) functions as a molecular chaperone, aiding in the synthesis of sarcoplasmic reticulum (SR) Ca(2+)-ATPase. This protein facilitates the proper maturation and expression of the SR Ca(2+)-ATPase.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Cell Biology

Background:

  • The beta-subunit of H(+)/K(+)-ATPase is recognized by a monoclonal antibody (mAbHKbeta).
  • This antibody cross-reacts with a protein involved in the maturation of sarcoplasmic reticulum (SR) Ca(2+)-ATPase.
  • Understanding chaperones for SR Ca(2+)-ATPase is crucial for cellular calcium regulation.

Purpose of the Study:

  • To identify the mAbHKbeta-reactive protein.
  • To investigate the role of this protein as a molecular chaperone for SR Ca(2+)-ATPase.
  • To elucidate the mechanism by which this chaperone influences SR Ca(2+)-ATPase synthesis.

Main Methods:

  • Partial purification of a 65-kDa protein from Xenopus ovary.
  • In-gel digestion and peptide sequencing for protein identification.
  • cRNA injection into Xenopus oocytes to study protein expression.
  • Immunoprecipitation and pulse-chase experiments to assess protein association and synthesis.

Main Results:

  • The 65-kDa protein was identified as methionine aminopeptidase II (MetAP2).
  • MetAP2 was found to be transiently associated with nascent SR Ca(2+)-ATPase.
  • MetAP2 facilitated the synthesis of functional SR Ca(2+)-ATPase.
  • An antibody against MetAP2 inhibited SR Ca(2+)-ATPase synthesis.

Conclusions:

  • MetAP2 acts as a molecular chaperone for the synthesis of SR Ca(2+)-ATPase.
  • This interaction is critical for the proper maturation and functional expression of SR Ca(2+)-ATPase.
  • MetAP2 plays a significant role in regulating calcium handling within the cell.

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