An “up-promoter” mutation affecting the acetamidase of Aspergillus nidulans

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Abstract
A derivative of an areA200 strain of Aspergillus nidulans selected for strong growth on acetamide as the sole nitrogen source was found to have a mutation, amd-18, closely linked to amdS, the acetamidase structural gene. This mutation results in 2–3 fold higher acetamidase activities than wildtype strains in uninduced as well as induced cultures. The effects of the amd-18 mutation are superimposed on the effects of other regulatory mutations affecting the acetamidase. The amd-18 mutation is cis-dominant with respect to the amdS gene. Immunological and gel electrophoresis studies have shown that amd-18 strains produce higher levels of acetamidase protein. A previously described cis-dominant mutation, amd19, also causes elevated levels of acetamidase protein. The amd-18 mutation may affect a promoter site for the amdS gene allowing an increased frequency of transcription.