The NAD-dependent malic enzyme of Arabidopsis thaliana: two proteins with different properties

TRONCONI, M.; MAURINO VG,; DRINCOVICH MF,; CARLOS SANTIAGO ANDREO

Rosario

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular, SAIB.; 2006

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

The mitochondrial NAD-dependent malic enzyme of plants (NAD-ME) has been suggested to be a heterodimer of á and â subunits. At present, several isoforms have been purified and characterized, but none of them in a recombinant manner. Alignment analysis based on Solanum tuberosum NAD-ME subunits cDNA sequence showed that Arabidopsis thaliana genome contains two putative nad-me genes. The predicted aminoacid sequences of á and â subunits showed 62% identity. A multiple sequence alignment among plant NAD-ME showed that á and â subunits are clustered in different groups. In this work, cDNA encoding the á and â subunits of the A. thaliana NAD-ME were cloned, expressed in a prokaryotic system and the proteins obtained structurally and biochemically characterized. Contrary to that previously reported, the separated subunits showed NAD-ME activity. The á subunit showed sensitivity to the activator CoA and a dimeric native aggregation state. The â subunit was not activated by CoA and presented a tetrameric native oligomeric state. In order to evaluate the a-b interactions in-vitro, both subunits were also co-expressed. The results indicate the possibility of the existence of two separate proteins with NAD-ME activity within Arabidopsis thaliana mitochondrias