Dimers or tetramers: oligomeric states of NADP Malic Enzyme of maize

MARIANA SAIGO; ENRIQUE DETARSIO; CLARISA ALVAREZ; DAMIÁN SAAVEDRA; VERÓNICA MAURINO; MARÍA FABIANA DRINCOVICH; CARLOS ANDREO

Mar del Plata

Congreso; Sociedad Argentina de Investigación en Bioquímica y Biología molecular XLIII Reunión anual; 2007

Sociedad Argentina de Investigación en Bioquímica y Biología molecular

NADP dependent Malic Enzyme (NADP-ME) is widely distributed in nature. It has been reported that in the native state the most active forms are usually tetramers. Dimers and monomers can also be found while they are present in lower amounts. Maize NADP-ME protein family has long being studied due to the essential role of one of the isoforms in carbon fixation. Even though the sequences in maize are well conserved, the photosynthetic isoform (ZmME1) is more closely related to a plastidic enzyme associated with housekeeping functions (ZmME2). Both isoforms have been compared with regard to their kinetics and structural features. Interestingly, the most abundant form of ZmME2 is dimeric, as has been shown by studies in recombinant systems. The aim of this work was to study the structural bases related to the oligomeric state of these isoforms. In the first place, the native conformation of ZmME1 and ZmME2 were assayed in plastids and cytosol of Arabidopsis thaliana. Both proteins conserved the same oligomeric states as shown previously, but ZmME2 displayed multiple conformations in the cytosol, most probably due to the association with another protein. Additionally, based on previous reports, we identified a small group of residues that are most probably responsible for the differences in the subunits interactions in ZmME1 and ZmME2.