Two PKA RIα holoenzyme states define ATP as an isoform-specific orthosteric inhibitor that competes with the allosteric activator, cAMP

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 116; no. 33; pp. 16347 - 16356
• Main Authors: Lu, Tsan-Wen, Wu, Jian, Aoto, Phillip C., Weng, Jui-Hung, Ahuja, Lalima G., Sun, Nicholas, Cheng, Cecilia Y., Zhang, Ping, Taylor, Susan S.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 13.08.2019
• Series: PNAS Plus
• Subjects: Activation; Adenosine Triphosphate - chemistry; Adenosine Triphosphate - genetics; Allosteric properties; Allosteric Regulation - genetics; Amino Acid Sequence - genetics; ATP; Biological Sciences; Catalysis; Crosstalk; Crystallography, X-Ray; Cyclic AMP; Cyclic AMP - chemistry; Cyclic AMP - genetics; Cyclic AMP-Dependent Protein Kinase RIalpha Subunit - chemistry; Cyclic AMP-Dependent Protein Kinase RIalpha Subunit - genetics; Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit - chemistry; Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit - genetics; Cyclic AMP-Dependent Protein Kinases - chemistry; Cyclic AMP-Dependent Protein Kinases - genetics; Dimers; Gene Expression Regulation, Enzymologic - genetics; Holoenzymes - chemistry; Holoenzymes - genetics; Humans; Interfaces; Isoforms; Kinases; Magnesium; PNAS Plus; Protein Binding - genetics; Protein kinase A; Protein Structure, Quaternary; Protein Subunits - chemistry; Protein Subunits - genetics; Signal Transduction - genetics; Substrates; structural biology; isoform-specific quaternary structure; allosteric and orthosteric regulation; cAMP; protein kinase A
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1906036116

Protein kinase A (PKA) holoenzyme, comprised of a cAMP-binding regulatory (R)-subunit dimer and 2 catalytic (C)-subunits, is the master switch for cAMP-mediated signaling. Of the 4 R-subunits (RIα, RIβ, RIIα, RIIβ), RIα is most essential for regulating PKA activity in cells. Our 2 RIα₂C₂ holoenzyme states, which show different conformations with and without ATP, reveal how ATP/Mg2+ functions as a negative orthosteric modulator. Biochemical studies demonstrate how the removal of ATP primes the holoenzyme for cAMP-mediated activation. The opposing competition between ATP/cAMP is unique to RIα. In RIIβ, ATP serves as a substrate and facilitates cAMP-activation. The isoform-specific RI-holoenzyme dimer interface mediated by N3A–N3A′ motifs defines multidomain cross-talk and an allosteric network that creates competing roles for ATP and cAMP. Comparisons to the RIIβ holoenzyme demonstrate isoform-specific holoenzyme interfaces and highlights distinct allosteric mechanisms for activation in addition to the structural diversity of the isoforms.