MP1: A MEK Binding Partner That Enhances Enzymatic Activation of the MAP Kinase Cascade

Science  11 Sep 1998:
Vol. 281, Issue 5383, pp. 1668-1671
DOI: 10.1126/science.281.5383.1668

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Signal transduction is controlled both by regulation of enzyme activation and by organization of enzymatic complexes with nonenzymatic adapters, scaffolds, and anchor proteins. The extracellular signal–regulated kinase (ERK) cascade is one of several evolutionarily conserved mitogen-activated protein (MAP) kinase cascades important in the regulation of growth, apoptosis, and differentiation. A two-hybrid screen was conducted to identify nonenzymatic components of this signaling cascade that might be important in regulating its activity. A protein called MP1 (MEK Partner 1) was identified that bound specifically to MEK1 and ERK1 and facilitated their activation. When overexpressed in cultured cells, MP1 enhanced activation of ERK1 and activation of a reporter driven by the transcription factor Elk-1. Expression of MP1 in cells increased binding of ERK1 to MEK1. MP1 apparently functions as an adapter to enhance the efficiency of the MAP kinase cascade.

  • * These authors contributed equally to this report.

  • Present address: Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.

  • Present address: European Molecular Biology Laboratory, Developmental Biology, 69012 Heidelberg, Germany.

  • § To whom correspondence should be addressed. E-mail: MJW{at}

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