Maize NADP-malate dehydrogenase: cDNA cloning, sequence, and mRNA characterization

We report here the isolation, characterization and nucleotide sequence of clones encoding the maize chloroplastic NADP-malate dehydrogenase (NADP-MDH) which functions in the C4 cycle of photosynthesis. A nearly full-length NADP-MDH cDNA clone was isolated using antibodies against the purified protein. This clone hybridizes to a 1600 base mRNA that is eight times more abundant in light-grown maize leaves than in etiolated leaves. Transcription in leaves begins 230 bp upstream of the predicted start of translation, as shown by primer extension experiments. The encoded amino acid sequence predicts that NADP-MDH is synthesized as a preprotein of 432 amino acids (46 865 Da) which is processed into a mature protein of 375 amino acids (40 934 Da) with removal of a 57 amino acid transit peptide (5 931 Da). We identify regions of similarity between the maize NADP-MDH and other MDH polypeptides.