Structural characterization of Ca2+/CaM in complex with the phosphorylase kinase PhK5 peptide

Atlanta G Cook, Louise N Johnson, James M McDonnell

Research output: Contribution to journalArticlepeer-review


Phosphorylase kinase (PhK) is a large hexadecameric enzyme consisting of four copies of four subunits: (alphabetagammadelta)4. An intrinsic calmodulin (CaM, the delta subunit) binds directly to the gamma protein kinase chain. The interaction site of CaM on gamma has been localized to a C-terminal extension of the kinase domain. Two 25-mer peptides derived from this region, PhK5 and PhK13, were identified previously as potential CaM-binding sites. Complex formation between Ca2+/CaM with these two peptides was characterized using analytical gel filtration and NMR methods. NMR chemical shift perturbation studies showed that while PhK5 forms a robust complex with Ca2+/CaM, no interactions with PhK13 were observed. 15N relaxation characteristics of Ca2+/CaM and Ca2+/CaM/PhK5 complexes were compared with the experimentally determined structures of several Ca2+/CaM/peptide complexes. Good fits were observed between Ca2+/CaM/PhK5 and three structures: Ca2+/CaM complexes with peptides from endothelial nitric oxide synthase, with smooth muscle myosin light chain kinase and CaM kinase I. We conclude that the PhK5 site is likely to have a direct role in Ca2+-regulated control of PhK activity through the formation of a classical 'compact' CaM complex.
Original languageEnglish
Pages (from-to)1511-22
Number of pages12
JournalFebs Journal
Issue number6
Publication statusPublished - 2005


  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • Calcium
  • Calmodulin
  • Catalytic Domain
  • Humans
  • Kinetics
  • Models, Molecular
  • Molecular Sequence Data
  • Phosphorylase Kinase
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Secondary
  • Protein Subunits


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