6HYI

Regulatory subunit of a cAMP-independent protein kinase A from Trypanosoma cruzi at 1.4 A resolution in complex with inosine

Summary for 6HYI

• Entry DOI: 10.2210/pdb6hyi/pdb
• Related: 6FTF
• Descriptor: Protein kinase A regulatory subunit, INOSINE (3 entities in total)
• Functional Keywords: protein kinase a, regulatory subunit, cell signalling, signaling protein
• Biological source: Trypanosoma cruzi
• Total number of polymer chains: 1
• Total formula weight: 35012.51

Authors

Volpato Santos, Y.,Lorentzen, E.,Basquin, J.,Boshart, M. (deposition date: 2018-10-22, release date: 2019-11-13, Last modification date: 2024-04-10)

Primary citation

Ober, V.T.,Githure, G.B.,Volpato Santos, Y.,Becker, S.,Moya Munoz, G.,Basquin, J.,Schwede, F.,Lorentzen, E.,Boshart, M.
Purine nucleosides replace cAMP in allosteric regulation of PKA in trypanosomatid pathogens.
Elife, 12:-, 2024

PubMed Abstract: Cyclic nucleotide binding domains (CNB) confer allosteric regulation by cAMP or cGMP to many signaling proteins, including PKA and PKG. PKA of phylogenetically distant is the first exception as it is cyclic nucleotide-independent and responsive to nucleoside analogues (Bachmaier et al., 2019). Here, we show that natural nucleosides inosine, guanosine and adenosine are nanomolar affinity CNB ligands and activators of PKA orthologs of the important tropical pathogens , and . The sequence and structural determinants of binding affinity, -specificity and kinase activation of PKAR were established by structure-activity relationship (SAR) analysis, co-crystal structures and mutagenesis. Substitution of two to three amino acids in the binding sites is sufficient for conversion of CNB domains from nucleoside to cyclic nucleotide specificity. In addition, a trypanosomatid-specific C-terminal helix (αD) is required for high affinity binding to CNB-B. The αD helix functions as a lid of the binding site that shields ligands from solvent. Selectivity of guanosine for CNB-B and of adenosine for CNB-A results in synergistic kinase activation at low nanomolar concentration. PKA pulldown from rapid lysis establishes guanosine as the predominant ligand in vivo in bloodstream forms, whereas guanosine and adenosine seem to synergize in the procyclic developmental stage in the insect vector. We discuss the versatile use of CNB domains in evolution and recruitment of PKA for novel nucleoside-mediated signaling.

PubMed: 38517938
DOI: 10.7554/eLife.91040

Experimental method

X-RAY DIFFRACTION (1.3994484654 Å)