These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Phosphorylation of sites 3 and 4 in rabbit skeletal muscle glycogen synthase by cAMP-dependent protein kinase.
    Author: Sheorain VS, Corbin JD, Soderling TR.
    Journal: J Biol Chem; 1985 Feb 10; 260(3):1567-72. PubMed ID: 2981863.
    Abstract:
    Rabbit skeletal muscle glycogen synthase (synthase a) can be phosphorylated by 0.2 to 2.5 microM catalytic subunit of cAMP-dependent protein kinase to a stoichiometry of 1.5 to 3 mol of 32PO4/subunit (90,000 X g). When a complete tryptic digest of this 32P-synthase was chromatographed on reverse phase high performance liquid chromatography, it was observed that, in addition to sites 1a, 1b, and 2, site 3 was phosphorylated. The peptide containing site 5 also contained 32PO4, but sequence analysis identified a new phosphorylation site, site 4 (Arg-His-Ser-Ser(PO4)-) which precedes site 5. Phosphorylation of sites 3 and 4 became significant when the total phosphorylation stoichiometry exceeded 1.5 mol/subunit. The heat-stable protein kinase inhibitor protein or the regulatory subunit of cAMP-dependent protein kinase decreased the phosphorylation of all sites, including sites 3 and 4. Phosphorylation of all sites by the holoenzyme form of cAMP-dependent kinase was highly dependent on the presence of cAMP. These results establish that phosphorylation of these sites is due to the cAMP-dependent protein kinase itself and not to a contaminating kinase(s). Synthase b from control rabbit muscle, containing 2 to 2.5 mol of phosphate/subunit, incorporated up to 2.0 mol of 32PO4 catalyzed in vitro by the cAMP-dependent protein kinase. Again, significant 32PO4 was detected in sites 3 and 4 as well as in 1a, 1b, and 2. These results suggest that the in vivo phosphorylation of sites 1a, 1b, 2, and 3 observed after injection of epinephrine in rabbits could be due solely to the known activation of the cAMP-dependent protein kinase.
    [Abstract] [Full Text] [Related] [New Search]