CORRECT INTRON SPLICING GENERATES A NEW TYPE OF A PUTATIVE ZINC-BINDING DOMAIN IN A TRANSCRIPTIONAL ACTIVATOR OF ASPERGILLUS-NIDULANS

alcR is the pathway-specific transcriptional activator of the ethanol regulon in the filamentous fungus, Aspergillus nidulans. The deduced amino acid sequence of a cDNA clone, including the 5' part of the alcR-mRNA, shows that a putative Zn-binding domain of the all-cysteine class, exemplified by GAL4 is present. This structure presents some striking features. At variance with other structures of this class, the binding domain is strongly asymmetrical. Model building indicates that the zinc-binding motif of alcR could adopt an helix-turn-helix structure. We propose that the DNA-binding motif of alcR could participate in two types of DNA-binding structures: the zinc-cluster and the helix-turn-helix.