A revised model for AMP-activated protein kinase structure: The alpha-subunit binds to both the beta- and gamma-subunits although there is no direct binding between the beta- and gamma-subunits.
The 5'-AMP-activated protein kinase (AMPK) is a master sensor for cellular metabolic energy state. It is activated by a high AMP/ATP ratio and leads to metabolic changes that conserve energy and utilize alternative cellular fuel sources. The kinase is composed of a heterotrimeric protein complex containing a catalytic alpha-subunit, an ... AMP-binding gamma-subunit, and a scaffolding beta-subunit thought to bind directly both the alpha- and gamma-subunits. Here, we use coimmunoprecipitation of proteins in transiently transfected cells to show that the alpha2-subunit binds directly not only to the beta-subunit, confirming previous work, but also to the gamma1-subunit. Deletion analysis of the alpha2-subunit reveals that the C-terminal 386-552 residues are sufficient to bind to the beta-subunit. The gamma1-subunit binds directly to the alpha2-subunit at two interaction sites, one within the catalytic domain consisting of alpha2 amino acids 1-312 and a second within residues 386-552. Binding of the alpha2 and the gamma1-subunits was not affected by 400 mum AMP or ATP. Furthermore, we show that the beta-subunit C terminus is essential for binding to the alpha2-subunit but, in contrast to previous work, the beta-subunit does not bind directly to the gamma1-subunit. Taken together, this study presents a new model for AMPK heterotrimer structure where through its C terminus the beta-subunit binds to the alpha-subunit that, in turn, binds to the gamma-subunit. There is no direct interaction between the beta- and gamma-subunits.
Mesh Terms:
AMP-Activated Protein Kinases, Adenosine Triphosphate, Binding Sites, Blotting, Western, Catalytic Domain, Cell Line, Cloning, Molecular, DNA Primers, DNA, Complementary, Gene Deletion, Humans, Multienzyme Complexes, Protein Binding, Protein Structure, Secondary, Protein Structure, Tertiary, Protein-Serine-Threonine Kinases, Transfection
AMP-Activated Protein Kinases, Adenosine Triphosphate, Binding Sites, Blotting, Western, Catalytic Domain, Cell Line, Cloning, Molecular, DNA Primers, DNA, Complementary, Gene Deletion, Humans, Multienzyme Complexes, Protein Binding, Protein Structure, Secondary, Protein Structure, Tertiary, Protein-Serine-Threonine Kinases, Transfection
J. Biol. Chem.
Date: Nov. 24, 2006
PubMed ID: 17012231
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