Isolation and Characterization of a cDNA That Encodes Maize Glutamate Dehydrogenase

A full-length cDNA clone, pMGDHl, encoding maize NADH-glutamatedehydrogenase (NADH-GDH) was isolated from a maize root cDNAlibrary. The identity of the cDNA was established by the coincidenceof the structure of the purified protein with that inferredfrom the nucleotide sequence of the cDNA. pMGDHl had a cDNAinsert of 1,638 bp and the open reading frame encoded 411 aminoacid residues. The deduced amino acid sequence was similar toputative partial sequences of GDHs from higher plants and tothe sequences of GDHs from organisms as diverse as mammals andbacteria. The NH₂-terminal sequence deduced from the open readingframe had a typical structure that is associated with the importof proteins into the mitochondrial matrix. The cDNA hybridizedto an RNA of about 1.6 kb. This transcript was more abundantin roots than in leaves and was localized in the bundle sheathcells in leaf tissues. Analysis of genomic DNA by Southern hybridizationsuggested the existence of gene(s) for another NADHGDH subunit(s). ²Present address: Biochemical Research Laboratories, Ezaki GlicoCo., Ltd.4-6-5 Utajima, Nishiyodogawa-ku, Osaka, 555 Japan