Mitochondrial aspartate aminotransferase ( maa1 ) inactivation causes glutamate-requiring glu1 mutation in Schizosaccharomyces pombe.

Two genomic genes, which rescue ammonium assimilation defect in the glutamate-requiring Schizosaccharomyces pombe glu1 mutant, were identified. The maa1 , encoding a mitochondrial aspartate aminotransferase, is the causative gene of glu1 mutation because an inseparable linkage between maa1 and glu1 on the chromosome, and also the glu1 mutant strain has a nonsense mutation within the maa1 coding region, which is responsible for its defective phenotype. The yhm2 , a mitochondrial 2-oxoglutarate carrier, was also isolated as a weak multicopy suppressor gene. These findings reiterate the importance of the mitochondria in utilizing the amino acids for cellular nitrogen metabolism.