COMPARISON OF EXPRESSION, LOCALIZATION AND KINETICS OF PKA CATALYTIC SUBUNITS IN S.CEREVISIAE

RECOUVREUX, V.; MORENO, S.; PORTELA, P.

Mar del Plata, Buenos Aires

Congreso; 43 Reunion Anual SAIB; 2007

SAIB

Our aim is to study the complexity of the activation mechanism of PKA in S.cerevisiae focusing on the contribution of specificity of the three different isoforms (Tpk1, Tpk2 and Tpk3) of catalytic subunit in this process. Our data suggests a specificity of signaling through the three PKA catalytic subunits in yeast. We found differences in the subcellular localization of each Tpk isoform in response to carbon sources and phase of growth. In exponential phase on glucose both Bcy1 (regulatory subunit of PKA) and Tpk2 displayed a nuclear-cytoplasmic localization whereas Tpk1 and Tpk3 showed a pattern with a higher proportion of cells with exclusive cytoplasmic localization. In exponential phase on glycerol and stationary phase of growth, the PKA subunits showed a cytoplasmatic localization, except Tpk3 that with a cytoplasmic punctuate pattern on stationary phase. Analysis of expression levels followed the order: Bcy1>Tpk1>Tpk2>Tpk3 during the exponential phase on glucose, whereas Tpk3=Tpk2 on glycerol and Tpk1> Bcy1 on stationary phase. The kinetic properties of purified Tpk1 and Tpk2 showed differences in the specificity constant toward synthetic peptide substrates, suggesting that Tpk2 has a higher catalytic efficiency. We propose that the combination of different properties of each Tpk isoform could operate as a control mechanism for the diversification of the PKA response.