Phosphorylation of telokin by cyclic nucleotide kinases and the identification of in vivo phosphorylation sites in smooth muscle

FEBS Lett. 2000 Aug 18;479(3):83-8. doi: 10.1016/s0014-5793(00)01884-6.


The Ca(2+)-independent acceleration of dephosphorylation of the regulatory light chain of smooth muscle myosin and relaxation of smooth muscle by telokin are enhanced by cyclic nucleotide-activated protein kinase(s) [Wu et al. (1998) J. Biol. Chem. 273, 11362-113691. The purpose of this study was to determine the in vivo site(s) and in vitro rates of telokin phosphorylation and to evaluate the possible effects of sequential phosphorylation by different kinases. The in vivo site(s) of phosphorylation of telokin were determined in rabbit smooth muscles of longitudinal ileum and portal vein. Following stimulation of ileum with forskolin (20 microM) the serine at position 13 was the only amino acid to exhibit increased phosphorylation. Rabbit portal vein telokin was phosphorylated on both Ser-13 and -19 as a result of forskolin and GTPgammaS stimulation in vivo. Point mutation of Ser-13 (to Ala or Asp) abolished in vitro phosphorylation by cyclic nucleotide-dependent protein kinases.

Publication types

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

MeSH terms

  • Animals
  • Colforsin / pharmacology
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • Cyclic GMP-Dependent Protein Kinases
  • Detergents / pharmacology
  • Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
  • Ileum / metabolism
  • MAP Kinase Signaling System*
  • Muscle Proteins / metabolism*
  • Muscle, Smooth / metabolism*
  • Myosin-Light-Chain Kinase
  • Octoxynol / pharmacology
  • Peptide Fragments
  • Peptides
  • Phosphorylation
  • Point Mutation
  • Portal Vein / metabolism
  • Protein Kinases / metabolism*
  • Rabbits
  • Recombinant Proteins / metabolism
  • Serine Endopeptidases / metabolism
  • Time Factors


  • Detergents
  • Muscle Proteins
  • Peptide Fragments
  • Peptides
  • Recombinant Proteins
  • Colforsin
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • telokin
  • Octoxynol
  • Protein Kinases
  • Cyclic AMP-Dependent Protein Kinases
  • Cyclic GMP-Dependent Protein Kinases
  • Myosin-Light-Chain Kinase
  • Serine Endopeptidases
  • lysyl endopeptidase