The MAPK kinase Pek1 acts as a phosphorylation-dependent molecular switch.

The mitogen-activated protein kinase (MAPK) pathway is a highly conserved eukaryotic signalling cascade that converts extracellular signals into various outputs, such as cell growth and differentiation. MAPK is phosphorylated and activated by a specific MAPK kinase (MAPKK): MAPKK is therefore considered to be an activating regulator of MAPK. Pmk1 is ...
a MAPK that regulates cell integrity and which, with calcineurin phosphatase, antagonizes chloride homeostasis in fission yeast. We have now identified Pek1, a MAPKK for Pmk1 MAPK. We show here that Pek1, in its unphosphorylated form, acts as a potent negative regulator of Pmk1 MAPK signalling. Mkh1, an upstream MAPKK kinase (MAPKKK), converts Pek1 from being an inhibitor to an activator. Our results indicate that Pek1 has a dual stimulatory and inhibitory function which depends on its phosphorylation state. This switch-like mechanism could contribute to the all-or-none physiological response mediated by the MAPK signalling pathway.
Mesh Terms:
Amino Acid Sequence, Calcium-Calmodulin-Dependent Protein Kinases, Cell Cycle Proteins, Enzyme Activation, Enzyme Inhibitors, Fungal Proteins, MAP Kinase Kinase 1, Mitogen-Activated Protein Kinase Kinases, Mitogen-Activated Protein Kinases, Molecular Sequence Data, Phosphorylases, Protein Kinases, Protein-Serine-Threonine Kinases, Schizosaccharomyces, Schizosaccharomyces pombe Proteins, Sequence Homology, Amino Acid, Signal Transduction
Nature
Date: Jun. 03, 1999
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