We have determined the complete DNA sequence of a segment derived from Drosophila melanogaster that complements a yeast adenine-8 (ade8) mutation. This sequence, in conjunction with transcriptional analysis, predicts that a 206 amino acid sequence accounts for complementation. We have ligated a 1.5 kb promoter segment of the yeast alcohol dehydrogenase I (ADHI) gene just upstream of the open reading frame. This construction results in ADE8+ function that responds to glucose and ethanol in a manner similar to that for the chromosomal ADHI gene, as determined by a simple quantitative color assay for ADE8+ function.