STRUCTURAL DETERMINANTS INVOLVED IN THE REDOX REGULATION OF THE Arabidopsis FUMARASES ENZYMES

ZUBIMENDI JP; MARIA PIA VALACCO; MORENO SILVIA; ANDREO CARLOS; DRINCOVICH, MF; TRONCONI, MA

Cordoba

Congreso; LII Reunion Anual SAIB; 2016

SAIB

Fumarase (FUM) is a homotetrameric enzyme that catalyzes thereversible hydration of fumarate to L-malate,a reaction of thetricarboxylic acid (TCA) cycle occurring in aerobic organisms. Inplants, the regulation of carbon flux through the TCA cycle isespecially important since mitochondrial activities have to becoordinated with photosynthesis. Arabidopsisthaliana has twoFUM genes, AtFUM1 encoding the mitochondrial isoform andAtFUM2 encoding for a cytosolic one. In previous studies, wehave carried out the biochemical characterization ofrecombinant forms of these enzymes. The emerged regulatoryproperties linked AtFUM1 and -2with the nitrogen metabolismand the cytosolic pH regulation. In this work, we have exploredthe redox modulation of AtFUMs, as several enzymes of TCAcycle have been reported as thiorredoxin targets in vitro. Inorder to identify the residues involved in the redox modulation,MALDI-TOFanalysis of oxidized and reduced AtFUMs as wellas site-directedmutagenesis approaches were performed. Theresults obtained for AtFUM1 indicated the participation ofCys219 and Cys306 in the formation of interchain disulfidebridges and suggested that Cys332, Cys389 and Cys435 arealso involved in the redox regulation. Our results provide newinsights into the regulatory mechanisms of FUM of plants thatcould link them with photosynthesis and other subcellular process