Isolation and structural organization of the Neurospora crassa copper metallothionein gene

The Neurospora crassa copper metallothionein gene was cloned and its complete nucleotide sequence is reported. Enriched metallothionein mRNA was used as a template for cDNA synthesis, primed by a metallothionein-specific, synthetic undecanucleotide. The sequence of the cDNA obtained allowed the synthesis of a unique 21-mer which was used to screen a genomic DNA library of N. crassa. In agreement with the published amino acid sequence, the gene codes for a polypeptide 26 amino acid residues in length. The coding region is interrupted by a small intron (94 nucleotides). The gene structure is compared with those of mammalian metallothioneins. In both cases, the coding regions are split by introns, the intron-exon boundaries, however, are in different positions. The neurospora copper metallothionein gene is, to our knowledge, the smallest gene interrupted by an intron isolated so far.