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Properties of MEKs, the kinases that phosphorylate and activate the extracellular signal-regulated kinases
Ist Teil von
The Journal of biological chemistry, 1993-11, Vol.268 (32), p.23933-23939
Ort / Verlag
Bethesda, MD: American Society for Biochemistry and Molecular Biology
Erscheinungsjahr
1993
Quelle
MEDLINE
Beschreibungen/Notizen
Activation of extracellular signal-regulated kinase (ERK) or mitogen-activated protein kinase by MEK (mitogen-activated protein
kinase or extracellular signal-regulated kinase kinase) is an essential event in the mitogenic growth factor signal transduction.
We now demonstrate that three recombinant MEKs (MEK1, MEK2, MEK3) show remarkably different activity toward recombinant ERK1
and ERK2. MEK2 is the most active ERK activator. The recombinant MEK1 has an activity approximately seven times lower than
that of MEK2. MEK3, which is identical to MEK1 except for missing an internal 26-amino acid residue and probably represents
an alternative splicing product of MEK1, shows neither autophosphorylation nor ERK-activating activity. Recombinant MEK1 and
MEK2 can be activated by epidermal growth factor-stimulated SWISS3T3 cell lysate. MEK1 and MEK2 can also be activated by autophosphorylation.
Autophosphorylation of MEKs correlates with their ability to phosphorylate and activate ERKs. Phosphorylation of MEK is also
stimulated by ERK. Phosphoamino acid analysis showed that ERK1 preferentially phosphorylated threonine residue of MEKs. MEKs
complex with ERKs in vitro. Interestingly, MEK3 also forms a complex with ERK1, although it is totally inactive as an ERK
activator.