Microtubule-associated protein 2 kinases, ERK1 and ERK2, undergo autophosphorylation on both tyrosine and threonine residues: Implications for their mechanism of activation

Rony Seger, Natalie G. Ahn, Teri G. Boulton, George D. Yancopoulos, Nikos Panayotatos, Elizabeth Radziejewska, Lowell Ericsson, Rebecca L. Bratlien, Melanie H. Cobb, Edwin G. Krebs

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Microtubule-associated protein 2 kinase (MAP kinase), which exists in several forms, is a protein serine/threonine kinase that participates in a growth factor-activated protein kinase cascade in which it activates a ribosomal protein S6 kinase (pp90rsk) while being regulated itself by a cytoplasmic factor (MAP kinase activator). Experiments with recombinant MAP kinase, ERK2, purified from Escherichia coli in a nonactivated form revealed a self-catalyzed phosphate incorporation into both tyrosine and threonine residues. Another MAP kinase, ERK1, purified from insulin-stimulated cells also autophosphorylated on tyrosine and threonine residues. Autophosphorylation of ERK2 correlated with its autoactivation, although both autophosphorylation and autoactivation were slow compared to that occurring in the presence of MAP kinase activator. Therefore, we propose that autophosphorylation is probably involved in the MAP kinase activation process in vitro, but it may not be sufficient for full activation. The specificity toward tyrosine and threonine residues indicates that the MAP kinases ERK1 and ERK2 are members of a group of kinases with specificity for tyrosine as well as serine and threonine residues.

Original languageEnglish (US)
Pages (from-to)6142-6146
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number14
Publication statusPublished - Jul 15 1991


ASJC Scopus subject areas

  • General
  • Genetics

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