Structure of the unliganded cAMP-dependent protein kinase catalytic subunit from Saccharomyces cerevisiae.
The structure of TPK1delta, a truncated variant of the cAMP-dependent protein kinase catalytic subunit from Saccharomyces cerevisiae, was determined in an unliganded state at 2.8 A resolution and refined to a crystallographic R-factor of 19.4%. Comparison of this structure to that of its fully liganded mammalian homolog revealed a highly conserved protein fold comprised of two globular lobes. Within each lobe, root mean square deviations in Calpha positions averaged approximately equals 0.9 A. In addition, a phosphothreonine residue was found in the C-terminal domain of each enzyme. Further comparison of the two structures suggests that a trio of conformational changes accompanies ligand-binding. The first consists of a 14.7 degrees rigid-body rotation of one lobe relative to the other and results in closure of the active site cleft. The second affects only the glycine-rich nucleotide binding loop, which moves approximately equals 3 A to further close the active site and traps the nucleotide substrate. The third is localized to a C-terminal segment that makes direct contact with ligands and the ligand-binding cleft. In addition to resolving the conformation of unliganded enzyme, the model shows that the salient features of the cAMP-dependent protein kinase are conserved over long evolutionary distances.
Mashhoon
N
N
Biophysics Program, Ohio State University Medical School, Columbus 43210, USA.
Carmel
G
G
Pflugrath
J W
JW
Kuret
J
J
D000595:Amino Acid Sequence; D002384:Catalysis; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010446:Peptide Fragments; D011487:Protein Conformation; D021122:Protein Subunits; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013379:Substrate Specificity
D008024:Ligands; D010446:Peptide Fragments; D021122:Protein Subunits; D017868:Cyclic AMP-Dependent Protein Kinases