Mammalian AMP-activated protein kinase shares structural and functional homology with the catalytic domain of yeast Snf1 protein kinase.
The AMP-activated protein kinase is responsible for the regulation of fatty acid synthesis by phosphorylation of acetyl-CoA carboxylase. It may also regulate cholesterol synthesis via phosphorylation and inactivation of hormone-sensitive lipase and hydroxymethylglutaryl-CoA reductase. We have purified the AMP-activated protein kinase 14,000-fold from porcine liver. The 63-kDa catalytic subunit co-purifies with two proteins of 40 and 38 kDa that may function as subunits. Partial amino acid sequence of the 63-kDa subunit revealed a striking homology with the catalytic domain of the yeast protein kinase transcriptional regulator Snf1 and its plant homologs. The Snf1 (72 kDa) and Snf4 (36 kDa) complex was also purified and found to phosphorylate the AMP-activated protein kinase peptide substrate, HMRSAMSGLHLVKRR-amide, but was not activated by AMP. Both Snf1/4 and the AMP-activated protein kinase phosphorylate and inactivate yeast acetyl-CoA carboxylase in vitro. These results indicate that during evolution the catalytic domain sequences of the Snf1 protein kinase subfamily have been exploited in the control of mammalian lipid metabolism and raise the possibilities that the AMP-activated protein kinase may have other substrates involved in regulating gene expression pathways, as well as Snf1 homologs participating in the control of lipid metabolism in many eukaryotic organisms.
Mitchelhill
K I
KI
St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia.
Stapleton
D
D
Gao
G
G
House
C
C
Michell
B
B
Katsis
F
F
Witters
L A
LA
Kemp
B E
BE
D055372:AMP-Activated Protein Kinases; D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D005656:Fungal Proteins / Q000737:chemistry; D008099:Liver / Q000201:enzymology*; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry*; D051381:Rats; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D005656:Fungal Proteins; D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D011494:Protein Kinases; C071570:SNF1-related protein kinases; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; D000103:Acetyl-CoA Carboxylase