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

SAIGO M; DETARSIO E; ALVAREZ CE; SAAVEDRA DD; MAURINO VG; DRINCOVICH MF; ANDREO CS

Mar del Plata

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2007

SAIB

DIMERS OR TETRAMERS: OLIGOMERIC STATES OFMAIZE NADPMALIC ENZYMESaigo M, Detarsio E , Alvarez CE , Saavedra DD , Maurino VG ,Drincovich MF , Andreo CSCEFOBI, Fac Cs Bioq y Farm, UNR; Instituto de Botánica UnivColonia, Alemania. E-mail: saigo@cefobi.gov.arArabidopsis thaliana.NADP dependent Malic Enzyme (NADP-ME) is widely distributedin nature. It has been reported that in the native state the most activeforms are usually tetramers. Dimers and monomers can also befound but they are present in lower amounts. Maize NADP-MEprotein family has long being studied due to the essential role of oneof the isoforms in carbon fixation. Even though the sequences inmaize are well conserved, the photosynthetic isoform (ZmME1) ismore closely related to a plastidic enzyme associated withhousekeeping functions (ZmME2). Both isoforms have beencompared with regard to their kinetics and structural features.Interestingly, the most abundant form of ZmME2 is dimeric, as hasbeen shown by studies in recombinant systems. The aim of this workwas to study the structural bases related to the oligomeric state ofthese isoforms. First, the native conformation of ZmME1 andZmME2 were assayed in plastids and cytosol of transgenic. Both proteins conserved the same oligomericstates as previously shown for the recombinant proteins, butZmME2 displayed multiple conformations in the cytosol, mostprobably due to the association with another protein. Additionally,based on previous reports, we identified a small group of residuesthat are most probably responsible for the differences in the subunitsinteractions in ZmME1 and ZmME2.