Protein kinase substrate recognition studied using the recombinant catalytic domain of AMP-activated protein kinase and a model substrate

J Mol Biol. 2002 Mar 22;317(2):309-23. doi: 10.1006/jmbi.2001.5316.

Abstract

We have expressed a truncated form of the alpha1 kinase domain of AMP-activated protein kinase (AMPK) in Escherichia coli as a glutathione-S-transferase fusion (GST-KD). A T172D mutant version did not require prior phosphorylation and was utilized for most subsequent studies. We have also created a recombinant substrate (GST-ACC) by expressing 34 residues around the major phosphorylation site (Ser79) on rat acetyl-CoA carboxylase-1/alpha (ACC1) as a GST fusion. This was an excellent substrate that was phosphorylated with similar kinetic parameters to ACC1 by both native AMPK and the bacterially expressed kinase domain. We also constructed a structural model for the binding of the ACC1 sequence to the kinase domain, based on crystal structures for related protein kinases. The model was tested by making a total of 25 mutants of GST-ACC and seven mutants of GST-KD, and measuring kinetic parameters with different combinations. The results reveal that AMPK and ACC1 interact over a much wider region than previously realized (>20 residues). The features of the interaction can be summarised as follows: (i) an amphipathic helix from P-16 to P-5 on the substrate binds in a hydrophobic groove on the large lobe of the kinase; (ii) basic residues at P-6 and P-4 bind to two acidic patches (D215/D216/D217 and E103/D100/E143, respectively), on the large lobe; (iii) a histidine at P+3 interacts with D56 on the small lobe; (iv) the side-chain of P+4 leucine could not be precisely positioned, but a new finding was that asparagine or glutamine could replace a hydrophobic residue at this position. These interactions position the serine residue to be phosphorylated in close proximity to the gamma-phosphate group of ATP. Although based on modelling rather than a determined structure, this represents one of the most detailed studies of the interaction between a kinase and its substrate achieved to date.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • AMP-Activated Protein Kinases
  • Acetyl-CoA Carboxylase / genetics
  • Acetyl-CoA Carboxylase / metabolism
  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • Catalytic Domain / genetics
  • Escherichia coli / genetics
  • Glutathione Transferase / genetics
  • Glutathione Transferase / metabolism
  • Histidine
  • Male
  • Models, Molecular
  • Molecular Sequence Data
  • Multienzyme Complexes / chemistry*
  • Multienzyme Complexes / genetics
  • Multienzyme Complexes / metabolism*
  • Mutation
  • Phosphorylation
  • Protein Conformation
  • Protein-Serine-Threonine Kinases / chemistry*
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Rats
  • Rats, Wistar
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Reproducibility of Results
  • Serine / metabolism
  • Substrate Specificity

Substances

  • Multienzyme Complexes
  • Recombinant Fusion Proteins
  • Serine
  • Histidine
  • Glutathione Transferase
  • Protein-Serine-Threonine Kinases
  • AMP-Activated Protein Kinases
  • Acetyl-CoA Carboxylase