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Nat Commun. 2019 Sep 4;10(1):3984. doi: 10.1038/s41467-019-11930-2.

Activation of PKA via asymmetric allosteric coupling of structurally conserved cyclic nucleotide binding domains.

Author information

1
Department of Chemistry, Georgetown University, Washington, DC, 20057, USA.
2
NEST, Istituto Nanoscienze del CNR and Scuola Normale Superiore, Pisa, 56127, Italy.
3
Astbury Centre & School of Molecular and Cellular Biology, University of Leeds, Leeds, LS2 9JT, UK.
4
Department of Molecular and Cellular Biology and Center for Precision Environmental Health, Baylor College of Medicine, Houston, Texas, 77030, USA.
5
Dan L Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, Texas, 77030, USA.
6
Center for Cancer Epigenetics, The University of Texas MD Anderson Cancer Center, Houston, Texas, 77030, USA.
7
Department of Bioengineering, Rice University, Houston, Texas, 77005, USA.
8
Department of Pharmacology, University of California, San Diego, La Jolla, California, 92093, USA.
9
Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California, 92093, USA.
10
Department of Chemistry, Georgetown University, Washington, DC, 20057, USA. rodrigo.maillard@georgetown.edu.

Abstract

Cyclic nucleotide-binding (CNB) domains allosterically regulate the activity of proteins with diverse functions, but the mechanisms that enable the cyclic nucleotide-binding signal to regulate distant domains are not well understood. Here we use optical tweezers and molecular dynamics to dissect changes in folding energy landscape associated with cAMP-binding signals transduced between the two CNB domains of protein kinase A (PKA). We find that the response of the energy landscape upon cAMP binding is domain specific, resulting in unique but mutually coordinated tasks: one CNB domain initiates cAMP binding and cooperativity, whereas the other triggers inter-domain interactions that promote the active conformation. Inter-domain interactions occur in a stepwise manner, beginning in intermediate-liganded states between apo and cAMP-bound domains. Moreover, we identify a cAMP-responsive switch, the N3A motif, whose conformation and stability depend on cAMP occupancy. This switch serves as a signaling hub, amplifying cAMP-binding signals during PKA activation.

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