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Deregulation of mitogen-activated protein kinase at low pH due to a structural rearrangement of activation segment

A A Tokmakov1, K I Sato, Y Fukami

  • 1Laboratory of Molecular Biology, Biosignal Research Center, Kobe University, Nada, Kobe, Japan. tokmak@kobe-u.ac.jp

Biochimica Et Biophysica Acta
|December 22, 1999
PubMed

Insights

Mitogen-activated protein kinase (MAPK) autophosphorylation increases at acidic pH, while its activity on other proteins decreases. This pH-dependent conformational change affects MAPK

Area of Science:

  • Biochemistry
  • Enzymology
  • Protein Kinase Regulation

Background:

  • Mitogen-activated protein kinase (MAPK) is a crucial signaling enzyme.
  • Enzyme activity is often modulated by environmental factors like pH.
  • Understanding MAPK regulation is vital for cellular signaling research.

Purpose of the Study:

  • To investigate the effect of pH on MAPK autophosphorylation and substrate phosphorylation.
  • To elucidate the structural basis for pH-dependent changes in MAPK activity.

Main Methods:

  • Recombinant MAPK autophosphorylation assays at varying pH.
  • Myelin basic protein phosphorylation assays.
  • Immunoprecipitation, ELISA, kinetic analysis, and reversible phosphorylation assays.

Main Results:

  • MAPK autophosphorylation was stimulated at weakly acidic pH (5.5-6.0).
  • Phosphorylation of myelin basic protein was inhibited below pH 6.0.
  • Low pH induced a conformational change in the MAPK activation segment, favoring autophosphorylation but inhibiting exogenous substrate phosphorylation.

Conclusions:

  • Acidic pH promotes a stable, low-activity conformation of MAPK.
  • This conformation facilitates intramolecular autophosphorylation while blocking the catalytic center for exogenous substrates.
  • pH-dependent conformational changes are critical for regulating MAPK activity and signaling.

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