The crystal structure of yeast regulatory subunit reveals key evolutionary insights into protein kinase A oligomerization

BARDECI, N; TOFOLON, E; TRAJTENBERG, F ; CARAMELO, J; LARRIEUX, N; ROSSI,S; BUSCHIAZZO, A; MORENO,S

JOURNAL OF STRUCTURAL BIOLOGY

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam; Año: 2021

1047-8477

Protein kinase A (PKA) is a widespread, ubiquitous enzyme that plays a key role in many signaling pathways from lower eukaryotes to metazoans. The regulatory (R) subunits provide spatiotemporal regulation of the catalytic activity by sequestering and targeting the catalytic (C) subunits to proper subcellular locations in a time and environment-dependent manner. This targeting is achieved through the dimerization and docking (D/D) domain, located at the N-terminus of the R subunits. The enzyme activation on the binding of the second messenger cAMP to two domains located at the C-terminus. While the structural diversity of the cAMP binding sites has been studied extensively, variability of the D/D domain across organisms remains poorly explored. The only available structures of these domains proceed from mammalian sources, where the R subunit is dimeric. Here we describe the first high resolution structure of a D/D domain from a non-mammalian species. The oligomeric state and the subcellular localization of Bcy1, the Saccharomyces cerevisiae R subunit, are different from its mammalian counterparts, but also dependent on the D/D domain. The structural analysis of the tetrameric D/D domain of Bcy1 we describe here provides key insights into the determinants of oligomerization of R subunits. By using a combination of phylogenetic analysis and site-directed mutagenesis, we found that not only Bcy1, but most fungi are likely to present tetrameric R subunits. This surprising finding challenges well-established concepts regarding the oligomeric state of these proteins and provides important insights into the structural diversity of this protein family. We also propose interesting working hypothesis regarding the variability of regulatory mechanisms across organisms.