Premium
Interaction of the GTP‐binding protein G i2 with a protein kinase A‐like kinase in mouse fibroblasts
Author(s) -
Crouch MICHAEL F.,
Jans DAVID A.,
Simson LJUBOV,
Hendry IAN A.
Publication year - 1995
Publication title -
australian and new zealand journal of medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.596
H-Index - 70
eISSN - 1445-5994
pISSN - 0004-8291
DOI - 10.1111/j.1445-5994.1995.tb02888.x
Subject(s) - mitogen activated protein kinase kinase , map2k7 , cyclin dependent kinase 2 , cyclin dependent kinase 9 , protein kinase a , map kinase kinase kinase , ask1 , c raf , cgmp dependent protein kinase , cyclin dependent kinase complex , protein kinase r , biochemistry , casein kinase 2 , cyclin dependent kinase 4 , microbiology and biotechnology , kinase , biology , chemistry
We have previously shown that the GTP‐binding protein, G i2 of mouse Balb/c3T3 cells is linked to a serine kinase which phosphorylates the a‐subunit of G i itself. In this report we show that G i , is coupled to a second protein kinase. This kinase does not phosphorylate G, but phosphorylates another protein bound non‐covalently to G i ‐. Phosphorylation of the G i ‐linked protein induces its release from G i . Kinase activity is slightly enhanced by G TP γ S, suggesting that this kinase may be physiologically regulated by G i . In an attempt to identify the kinase we have, examined the effect of peptide substrates and inhibitors on kinase activity. We found that the protein kinase A inhibitory peptide, PKI5‐24, inhibited the kinase activity, but at concentrations above those usually required to block protein kinase A. The protein kinase A substrate peptide, kemptide, acted as a substrate of the kinase, and was an inhibitor of the phosphorylation of the G‐linked protein. However, a protein kinase A, catalytic subunit antibody failed to react with any proteins linked to G i . A protein kinase C inhibitory peptide had no effect on phosphorylation of the G i ‐linked protein. Thus, the identity of this kinase has not been resolved, but it may form part of the signalling system of activated G i in fibroblasts.