INVESTIGADORES
ROSSI Silvia Graciela
congresos y reuniones científicas
Título:
KINETIC AND CATALYTIC MECHANISMS OF cAMP PROTEIN KINASE (PKA)
Autor/es:
RINALDI, J;; ROSSI,S.;; MORENO, S
Lugar:
Rosario, Santa Fe, Argentina
Reunión:
Congreso; SAIB 42nd Annual Meeting XLII Reunión Anual -Argentine Society for Biochemistry and Molecular Biology- -Sociedad Argentina de Investigación Bioquímica y Biología Molecular-; 2006
Institución organizadora:
SAIB
Resumen:
Like all Ser-Thr Protein Kinases, PKA is a ATP-dependent
phosphotransferase that delivers a single phospohryl group from
the ã position of ATP to the hydroxyls of a Ser or a Thr in protein
substrates. It is a heterotetramer composed of a regulatory
subunit dimer (R2) and two catalytic subunits (2C).The inhibitory
site (IS) of R subunit docks to the active site of C subunit. The
kinetic pathway for substrate phosphorylation by PKA is
composed of three fundamental events: substrate binding, the
phosphoryl transfer step, and irreversible net product release.
While the simple core structure is shared within the protein
kinases family, the core frequently interacts with regulatory
proteins or domains that either enhance or repress catalytic
function. For instance, biochemical assays perfomed with
synthetic peptides in PKA system have shown that the presence
of the 40-residue region N-terminal to the IS enhances the
activity of C subunit. To evaluate which of the reaction steps are
being affected by this region we have estimated the effect of
solvent viscosity on the kcat. kcat was fully sensitive to solvent
viscosity using kempide as substrate, indicating the rate-limiting
step is the net product release; while when using the peptide that
includes the N-terminal to the IS region the effect is intermediate,
implying that phosphoryl transfer and net product release are
both rate-determining.