PKA-I holoenzyme structure reveals a mechanism for cAMP-dependent activation.
Protein kinase A (PKA) holoenzyme is one of the major receptors for cyclic adenosine monophosphate (cAMP), where an extracellular stimulus is translated into a signaling response. We report here the structure of a complex between the PKA catalytic subunit and a mutant RI regulatory subunit, RIalpha(91-379:R333K), containing both cAMP-binding domains. Upon binding to the catalytic subunit, RI undergoes a dramatic conformational change in which the two cAMP-binding domains uncouple and wrap around the large lobe of the catalytic subunit. This large conformational reorganization reveals the concerted mechanism required to bind and inhibit the catalytic subunit. The structure also reveals a holoenzyme-specific salt bridge between two conserved residues, Glu261 and Arg366, that tethers the two adenine capping residues far from their cAMP-binding sites. Mutagenesis of these residues demonstrates their importance for PKA activation. Our structural insights, combined with the mutagenesis results, provide a molecular mechanism for the ordered and cooperative activation of PKA by cAMP.
Kim
Choel
C
Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0654, USA.
Cheng
Cecilia Y
CY
Saldanha
S Adrian
SA
Taylor
Susan S
SS
D000225:Adenine / Q000737:chemistry; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001120:Arginine / Q000737:chemistry; D001665:Binding Sites; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D000242:Cyclic AMP / Q000737:chemistry* / Q000378:metabolism; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D018698:Glutamic Acid / Q000737:chemistry; D020035:Holoenzymes / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D014364:Tryptophan / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry
D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D020035:Holoenzymes; D018698:Glutamic Acid; D014443:Tyrosine; D014364:Tryptophan; D001120:Arginine; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000225:Adenine