Mitogen-activated Swiss mouse 3T3 RSK kinases I and II are related to pp44mpk from sea star oocytes and participate in the regulation of pp90rsk activity Academic Article uri icon


MeSH Major

  • Protein Kinases
  • Ribosomal Protein S6 Kinases, 90-kDa
  • Starfish


  • Using a recombinant rsk gene product as a substrate for in vitro kinase assays, we have identified two mitogen-activated Swiss 3T3 RSK protein kinase activities (referred to as RSK kinase I and RSK kinase II, based on their order of elution from phenyl-Sepharose). Polyclonal antisera prepared against maturation-regulated 44-kDa myelin basic protein (MBP) kinase (pp44mpk) purified from sea star oocytes demonstrated immunocrossreactivity with polypeptides of approximately 44 kDa in the RSK kinase I preparation and approximately 42 kDa in the RSK kinase II preparation, respectively. These polypeptides were also recognized by anti-phosphotyrosine antibodies, and either phosphatase 1B or 2A (tyrosine- and serine/threonine-specific phosphatases, respectively) separately inactivated RSK phosphotransferase activity supporting the notion that tyrosine and serine/threonine phosphorylation are required for activity. In vitro, both RSK kinases and MBP kinase phosphorylated recombinant RSK and generated nearly identical two-dimensional tryptic phosphopeptide maps. They also phosphorylated MBP and microtubule-associated protein 2 but not 40S ribosomal protein S6. Furthermore, these protein kinases phosphorylated and partially activated pp90rsk in immune complexes obtained from quiescent cells.

publication date

  • June 1991



  • Academic Article



  • eng

PubMed Central ID

  • PMC51791

PubMed ID

  • 2052581

Additional Document Info

start page

  • 4981

end page

  • 5


  • 88


  • 11