Structural aspects of Bcy1, the regulatory subunit of PKA from Saccharomyces cerevisiae

FERNÁNDEZ NÚÑES, L; GONZÁLEZ BARDECI, N; BLUMENTAHL, D; TURJANSKI, A; ROSSI, S; MORENO, S

Potrero de Funes, San Luis

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2011

SAIB

Yeast is the first non-metazoan organism for which some structural information of PKA is available. Our group has obtained the crystal structure of the cAMP binding domains of Bcy1, the regulatory subunit of PKA. We now show results that contribute to understand the structure of the whole Bcy1 dimer. The solution structure of D140-Bcy1, as well as of whole Bcy1 have been solved by SAXS (small angle X-ray scattering). The R and D of the two structures g max were determined. The structure of D140-Bcy1 was modeled ab initio by using de DAMMIN program. The resulting structure compares very favorably with the crystal structure, thus confirming the particular relative orientation of A and B cAMP domains. The structure of whole Bcy1 seems to be more compact than the one of RI and RII. The amino termini of R subunits constitute the so called D/D domain, responsible for the dimerization of the subunits and for the interaction with anchoring proteins (AKAPs). Chemical crosslinking experiments confirm that Bcy1 exists as a dimer, via its N-terminus. The N terminus of Bcy1 was modeled by homology using Swiss Model and further minimization with GROMACS. The preliminary model shows that Bcy1 shares with its counterparts the residues important for dimerization; however the exposed surface, that should interact with anchoring proteins (not described yet in yeast) have characteristics of its own.