Mucor corcinelloides PKA, interaction between the R and C subunits

OCAMPO J; MORENO, S; ROSSI S

Rosario

Congreso; Sociedad Argentina de Bioquímica y Biología Molecular; 2006

SAIB

and C in M.circinelloides PKA is higher than in PKA from S. cereviciae and higher eukaryoticorganisms.In the range where the PKA activity was no longer proportional to enzymeconcentration, NaCl could increse the activity of the holoenzyme, indicating that completeholoenzyme disociation in vitro is not achived upon incubation with cAMP without NaCl. In acAMP-agarose purification of C subunit it was necessary to use ClNa to obtain this subunit. Ourhypothesis is that the N-terminal region of RM,which has acidic residues,is responsible for thedifference in the interaction.Wt R and R1 laking the N-terminal and R2 lacking a region of acidicresidues were cloned. Interaction between these Rs with C subunits was evaluated by in vitroinhibition or dissociation assays.The IC50 for wtR was lower than those for mutantRs.Dissociation of reconstituted holoenzyme showed that higher cAMP concentration wererequired to dissociate the wtR-C than to dissociate the mtR-C. The behaivour of CM or Cb wasdifferent.The results indicates that the acidic residues region may be important in the high affinityinteraction R-C found M.circinelloides PKA.