4DFZ

Role of N-terminal myristylation in the structure and regulation of cAMP-dependent protein kinase.

(2012) J Mol Biol 422: 215-229

• PubMed: 22617327 Search on PubMedSearch on PubMed Central
• DOI: https://doi.org/10.1016/j.jmb.2012.05.021
• Primary Citation of Related Structures:  
  4DFX, 4DFZ, 4DG0, 4DG2


• PubMed Abstract: 
  

  The catalytic (C) subunit of cAMP-dependent protein kinase [protein kinase A (PKA)] is a major target of cAMP signaling, and its regulation is of fundamental importance to biological processes. One mode of regulation is N-myristylation, which has eluded structural and functional characterization so far because most crystal structures are of the non-myristylated enzyme, are phosphorylated on Ser10, and generally lack electron density for the first 13 residues. We crystallized myristylated wild-type (WT) PKA and a K7C mutant as binary (bound to a substrate peptide) and ternary [bound to a substrate peptide and adenosine-5'-(β,γ-imido)triphosphate] complexes. There was clear electron density for the entire N-terminus in the binary complexes, both refined to 2.0 ?, and K7C ternary complex, refined to 1.35 ?. The N-termini in these three structures display a novel conformation with a previously unseen helix from residues 1 to 7. The K7C mutant appears to have a more stable N-terminus, and this correlated with a significant decrease in the B-factors for the N-terminus in the myr-K7C complexes compared to the WT binary complex. The N-terminus of the myristylated WT ternary complex, refined to 2.0 ?, was disordered as in previous structures. In addition to a more ordered N-terminus, the myristylated K7C mutant exhibited a 53% increase in k(cat). The effect of nucleotide binding on the structure of the N-terminus in the WT protein and the kinetic changes in the K7C protein suggest that myristylation or occupancy of the myristyl binding pocket may serve as a site for allosteric regulation in the C-subunit.

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Organizational Affiliation: 

Department of Pharmacology, University of California San Diego, San Diego, CA 92093, USA.