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Contributions of the mitogen-activated protein (MAP) kinase backbone and phosphorylation loop to MEK specificity

M J Robinson1, M Cheng, A Khokhlatchev

  • 1Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA.

The Journal of Biological Chemistry
|November 22, 1996
PubMed

Insights

Mitogen-activated protein kinase kinases (MEKs) show specific phosphorylation of MAP kinase family members. MEK1 and MEK2 phosphorylate ERK2 mutants, but only MEK2 phosphorylates ERK3, indicating other factors influence MEK specificity.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Biochemistry

Background:

  • Mitogen-activated protein kinase (MAPK) pathways are crucial for cellular processes.
  • Mitogen-activated protein kinase kinases (MEKs) are key regulators that activate MAPKs.
  • Understanding MEK specificity is vital for dissecting MAPK signaling networks.

Purpose of the Study:

  • To investigate the substrate specificity of different MEK isoforms.
  • To determine how modifications in the ERK2 phosphorylation loop affect MEK recognition.
  • To explore the phosphorylation of ERK3 by mammalian MEKs.

Main Methods:

  • Generation and characterization of ERK2 phosphorylation loop mutants.
  • In vitro phosphorylation assays using six mammalian MEK isoforms.
  • Comparison of MEK activity against wild-type and mutant MAP kinases.

Main Results:

  • MEK1 and MEK2 effectively phosphorylated most generated ERK2 mutants.
  • MEK2, but not MEK1, demonstrated the ability to phosphorylate ERK3.
  • Alterations within the ERK2 phosphorylation loop did not significantly alter MEK1/MEK2 activity or confer recognition by other MEKs.

Conclusions:

  • MEK1 and MEK2 exhibit distinct substrate specificities within the MAP kinase family.
  • Phosphorylation loop modifications alone do not fully explain MEK-MAPK recognition.
  • Additional, unidentified factors likely govern the precise specificity of MEK-MAPK interactions.

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