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A stimulated S6 kinase from rat liver: identity with the mitogen activated S6 kinase of 3T3 cells.
Author(s) -
Kozma S.C.,
Lane H.A.,
Ferrari S.,
Luther H.,
Siegmann M.,
Thomas G.
Publication year - 1989
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1989.tb08597.x
Subject(s) - cycloheximide , biology , protein kinase a , mitogen activated protein kinase kinase , kinase , microbiology and biotechnology , activator (genetics) , cyclin dependent kinase 2 , phosphorylation , phosphatase , map2k7 , biochemistry , protein biosynthesis , gene
A number of approaches were tested for their ability to induce S6 phosphorylation and S6 kinase activation in rat liver, including i.p. injection of insulin, sodium orthovanadate or cycloheximide, as well as refeeding starved animals. All treatments led to increased S6 phosphorylation and activation of the apparent same enzyme. The most potent activator of the S6 kinase in liver extracts was cycloheximide. Maximum activation was achieved in 20 min at 1 mg cycloheximide/100 g body weight, with half‐maximal activation in 10 min. Based on these findings a large‐scale kinase purification procedure was established involving seven steps of chromatography. Following the final step a major protein band of Mr 70,000 was revealed. The protein was purified 20,000‐fold, had a sp. act. of 640 nmol/min/mg of protein towards S6, autophosphorylated and was inactivated by phosphatase 2A. Peptide maps of autophosphorylated material were identical to those derived from the mitogen‐activated kinase of 3T3 cells.