THE LEU-1 GENE OF NEUROSPORA-CRASSA - NUCLEOTIDE AND DEDUCED AMINO-ACID-SEQUENCE COMPARISONS

The Neurospora crassa leu-1 gene encodes beta-isopropylmalate dehydrog enase (IPMDH; EC 1.1.1.85), an enzyme in the leucine biosynthetic path way. We determined the nucleotide sequence of the entire leu-1 gene an d of four independent cDNA clones. By comparing the genomic and cDNA s equences, four introns were identified in the 5' portion of the gene a nd a single open reading frame was established. One of the introns is located within the 5'-noncoding region of the transcript. The deduced amino acid sequence encoded by leu-1 was aligned with that of the homo logous yeast enzyme and extensive sequence identity was uncovered. The lesion present in a conventional leu-1 mutant was identified as the i nsertion of a single base pair.