Are SnRK1 Plant Protein Kinases Distinctively Regulated by Metabolites Under Light/Dark Conditions?

CLAUDIA V. PIATTONI; ALBERTO A. IGLESIAS; STEVEN C. HUBER

Potrero de los Funes, San Luis

Congreso; XLVII Reunión Anual de SAIB; 2011

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

SnRK1s are plant protein kinases related to yeast SNF1 andmammalian AMPK. These kinases are hetero-oligomeric proteinsof catalytic (a) and non-catalytic (b and g) subunits that would haveroles in regulation and targeting. SnRK1s play key roles as majorintegrators of energy signaling, growth, and carbon and nitrogenmetabolism. Previous works have shown that SnRK1 activity couldbe regulated by Glc6P, Tre6P and Rib5P depending on the plant andtissue involved. We wondered if regulation of SnRK1 by differentmetabolites could be related with the trophic characteristics and/orthe metabolic state of the plant tissue. In this work we purifiedSnRK1 kinases from Arabidopsis seedlings grown under light ordark conditions and we characterized its regulation by differentmetabolites. Rib5P and Rul5P behaved as strong inhibitors of theSnRK1 purified from seedlings grown under light but not underdark conditions. Characterization of SnRK1 inhibition suggeststhat Rib5P (I ~2 mM) and Rul5P (I ~100 μM) could act as 0.5 0.5competitive inhibitors respect to ATP. Several lines of evidencesuggest that inhibition by Rib5P is not the result of ATPconsumption, but the potential for this artifact remains to beunequivocally ruled out. We hypothesize that differentialregulation could be related with changes in SnRK1 subunit geneexpression patterns of the several coding genes.