Distal recognition sites in substrates are required for efficient phosphorylation by the cAMP-dependent protein kinase.
Protein kinases are important mediators of signal transduction in eukaryotic cells, and identifying the substrates of these enzymes is essential for a complete understanding of most signaling networks. In this report, novel substrate-binding variants of the cAMP-dependent protein kinase (PKA) were used to identify substrate domains required for efficient phosphorylation in vivo. Most wild-type protein kinases, including PKA, interact only transiently with their substrates. The substrate domains identified were distal to the sites of phosphorylation and were found to interact with a C-terminal region of PKA that was itself removed from the active site. Only a small set of PKA alterations resulted in a stable association with substrates, and the identified residues were clustered together within the hydrophobic core of this enzyme. Interestingly, these residues stretched from the active site of the enzyme to the C-terminal substrate-binding domain identified here. This spatial organization is conserved among the entire eukaryotic protein kinase family, and alteration of these residues in a second, unrelated protein kinase also resulted in a stable association with substrates. In all, this study identified distal sites in PKA substrates that are important for recognition by this enzyme and suggests that the interaction of these domains with PKA might influence specific aspects of substrate binding and/or release.
Program in Molecular, Cellular and Developmental Biology, The Ohio State University, Columbus, OH 43210, USA.
Stephen J
SJ
Deminoff
Vidhya
V
Ramachandran
Paul K
PK
Herman
D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity; D019892:eIF-2 Kinase / Q000737:chemistry / Q000378:metabolism; D020666:ras-GRF1 / Q000378:metabolism
C542351:CDC25 protein, S cerevisiae; D047908:Intracellular Signaling Peptides and Proteins; D029701:Saccharomyces cerevisiae Proteins; D020666:ras-GRF1; D017346:Protein Serine-Threonine Kinases; C062391:YAK1 protein, S cerevisiae; D019892:eIF-2 Kinase; D017868:Cyclic AMP-Dependent Protein Kinases