Requirement for negative charge on "activation loop" of protein kinase C

J Biol Chem. 1994 Nov 4;269(44):27715-8.


Increasing evidence has implicated a post-translational phosphorylation in the production of a catalytically competent protein kinase C. Here we present structural and biochemical evidence that Thr500 of protein kinase C-beta II is the residue phosphorylated by another kinase. Modeling studies indicate that this residue is part of a "lip" structure at the entrance of the catalytic site; phosphorylation on this lip, or "activation loop," is central to the regulation of three kinases whose structures have been elucidated (Taylor, S. S., and Radzio-Andzelm, E. (1994) Structure 2, 345-355). Biochemical data reveal that mutation of Thr500 to an acidic residue (Glu) results in expression of catalytically active protein kinase C in COS cells. In contrast, mutation of this residue to a neutral, non-phosphorylatable residue (Val) results in expression of inactive enzyme. Thus, negative charge at position 500 is required for catalytically competent protein kinase C-beta II. These data suggest that signal processing by protein kinase C cannot occur until the enzyme is first phosphorylated by a protein kinase C kinase.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • DNA Primers / chemistry
  • Glutamates / chemistry
  • In Vitro Techniques
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Phosphothreonine / chemistry
  • Protein Kinase C / chemistry*
  • Protein Structure, Tertiary
  • Recombinant Proteins
  • Structure-Activity Relationship
  • Threonine / chemistry


  • DNA Primers
  • Glutamates
  • Recombinant Proteins
  • Phosphothreonine
  • Threonine
  • Protein Kinase C