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Publication Abstract from PubMed

Protein kinases comprise the major enzyme family critically involved in signal transduction pathways; posttranslational modifications affect their regulation and determine signaling states. The prototype protein kinase A (PKA) possesses an N-terminal alpha-helix (Helix A) that is atypical for kinases and is thus a major distinguishing feature of PKA. Its physiological function may involve myristoylation at the N-terminus and modulation via phosphorylation at serine 10. Here we describe an unusual structure of an unmyristoylated PKA, unphosphorylated at serine 10, with a completely ordered N-terminus. Using standard conditions (e.g., PKI 5-24, ATP site ligand, MEGA-8), a novel 2-fold phosphorylated PKA variant showed the ordered N-terminus in a new crystal packing arrangement. Thus, the critical factor for structuring the N-terminus is apparently the absence of phosphorylation of Ser10. The flexibility of the N-terminus, its myristoylation, and the conformational dependence on the phosphorylation state are consistent with a functional role for myristoylation.

The typically disordered N-terminus of PKA can fold as a helix and project the myristoylation site into solution.,Breitenlechner C, Engh RA, Huber R, Kinzel V, Bossemeyer D, Gassel M Biochemistry. 2004 Jun 22;43(24):7743-9. PMID:15196017^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.