Post-translational Modifications of the beta-1 Subunit of AMP-activated Protein Kinase Affect Enzyme Activity and Cellular Localization

Biochem J. 2001 Mar 1;354(Pt 2):275-83. doi: 10.1042/0264-6021:3540275.


The AMP-activated protein kinase (AMPK) is a ubiquitous mammalian protein kinase important in the adaptation of cells to metabolic stress. The enzyme is a heterotrimer, consisting of a catalytic alpha subunit and regulatory beta and gamma subunits, each of which is a member of a larger isoform family. The enzyme is allosterically regulated by AMP and by phosphorylation of the alpha subunit. The beta subunit is post-translationally modified by myristoylation and multi-site phosphorylation. In the present study, we have examined the impact of post-translational modification of the beta-1 subunit on enzyme activity, heterotrimer assembly and subcellular localization, using site-directed mutagenesis and expression of subunits in mammalian cells. Removal of the myristoylation site (G2A mutant) results in a 4-fold activation of the enzyme and relocalization of the beta subunit from a particulate extranuclear distribution to a more homogenous cell distribution. Mutation of the serine-108 phosphorylation site to alanine is associated with enzyme inhibition, but no change in cell localization. In contrast, the phosphorylation site mutations, SS24, 25AA and S182A, while having no effects on enzyme activity, are associated with nuclear redistribution of the subunit. Taken together, these results indicate that both myristoylation and phosphorylation of the beta subunit of AMPK modulate enzyme activity and subunit cellular localization, increasing the complexity of AMPK regulation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • AMP-Activated Protein Kinases
  • Animals
  • COS Cells
  • Catalytic Domain / genetics
  • Green Fluorescent Proteins
  • Humans
  • Kinetics
  • Luminescent Proteins / metabolism
  • Multienzyme Complexes / chemistry
  • Multienzyme Complexes / genetics
  • Multienzyme Complexes / metabolism*
  • Mutagenesis, Site-Directed
  • Myristic Acid / metabolism
  • Phosphorylation
  • Protein Conformation
  • Protein Folding
  • Protein Processing, Post-Translational*
  • Protein Subunits
  • Protein-Serine-Threonine Kinases / chemistry
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Recombinant Fusion Proteins / metabolism
  • Structure-Activity Relationship


  • Luminescent Proteins
  • Multienzyme Complexes
  • Protein Subunits
  • Recombinant Fusion Proteins
  • Myristic Acid
  • Green Fluorescent Proteins
  • PRKAB1 protein, human
  • Protein-Serine-Threonine Kinases
  • AMP-Activated Protein Kinases