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.

			Author Information
			(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]

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