PubMed Journals: J Biol Chem
Source: PMID: 9305909
⇦ ⇨ J Biol Chem. 1997 Sep 26;272(39):24475-9.
Posttranslational modifications of the
5'-AMP-activated protein kinase beta1 subunit.
Mitchelhill KI(1), Michell BJ, House CM,
Stapleton D, Dyck J, Gamble J, Ullrich C,
Witters LA, Kemp BE.
(1) St. Vincent's Institute of Medical Research,
41 Victoria Parade, Fitzroy, Victoria 3065
The AMP-activated protein kinase (AMPK)
consists of catalytic alpha and noncatalytic
beta and gamma subunits and is responsible
for acting as a metabolic sensor for AMP
levels. There are multiple genes for each
subunit and the rat liver AMPK alpha1 and
alpha2 catalytic subunits are associated
with beta1 and gamma1 noncatalytic subunits.
We find that the isolated gamma1 subunit
is N-terminally acetylated with no other posttranslational
modification. The isolated beta1 subunit
is N-terminally myristoylated. Transfection
of COS cells with AMPK subunit cDNAs containing
a nonmyristoylatable beta1 reduces, but
does not eliminate, membrane binding of
AMPK heterotrimer. The isolated beta1 subunit
is partially phosphorylated at three sites,
Ser24/25, Ser182, and Ser108. The Ser24/25
and Ser108 sites are substoichiometrically
phosphorylated and can be autophosphorylated
in vitro. The Ser-Pro site in the sequence
LSSS182PPGP is stoichiometrically phosphorylated,
and no additional phosphate is incorporated
into this site with autophosphorylation.
Based on labeling studies in transfected
cells, we conclude that alpha1 Thr172 is
a major, although not exclusive, site of
both basal and stimulated alpha1 phosphorylation
by an upstream AMPK kinase.
PMID: 9305909 [Indexed for MEDLINE]