IAL   21557
INSTITUTO DE AGROBIOTECNOLOGIA DEL LITORAL
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Ostreococcus tauri ADP-glucose pyrophosphorylase: Insights into the activator binding site
Autor/es:
CARLOS M. FIGUEROA; MISTY L. KUHN; ALBERTO A. IGLESIAS; MIGUEL A. BALLICORA
Lugar:
Puerto Madryn, Argentina
Reunión:
Congreso; XLVI Reunión Anual de la SAIB; 2010
Institución organizadora:
Sociedad Argentina de Investigación en Bioquímica y BM
Resumen:
ADP-glucose
pyrophosphorylase (ADPGlcPPase) controls the synthesis of starch in plants and
algae. The enzyme from photosynthetic organisms is a heterotetramer, composed
of two small (S) and two large (L) subunits, and is mainly activated by
3-phosphoglycerate (3PGA), the first intermediary of the carbon fixation
pathway. To study the evolution of structure and function of subunits in the
ADPGlcPPase family, we synthesized the genes encoding for the S (OtaS)
and L (OtaL) subunits of the unicellular alga Ostreococcus tauri,
one of the most ancient eukaryotic species in the green lineage. An interesting
feature of the OtaL subunit is that a highly conserved Lys residue,
present in the OtaS subunit, demonstrated to be important for 3PGA
binding in the Anabaena ADPGlcPPase, is replaced by Arg. In this work,
we constructed the mutants OtaSK443R and OtaLR466K
and co-expressed them together or with the corresponding wild type subunits.
3PGA kinetics showed A0.5 values of 0.22, 0.58, 1.2 and 2.9
mM for OtaS/OtaLR466K, OtaS/OtaL, OtaSK443R/OtaLR466K
and OtaSK443R/OtaL, respectively. In addition, OtaSK443R/OtaL
displayed the lowest activation fold, thus confirming the importance of the
mutated Lys residue for 3PGA activation. Our results suggest that both subunits
evolved independently an adopted divergent activation properties associated
with metabolic differences present in each organism.