ISOLATION AND CHARACTERIZATION OF AN ASPERGILLUS-NIDULANS GENE ENCODING AN ALKALINE PROTEASE

We have cloned an Aspergillus nidulans gene (prtA) encoding an alkalin e protease (Alp) by probing an A. nidulans library with a fragment amp lified from an Aspergillus oryzae Alp-encoding gene. The nucleotide (n t) sequence of prtA was determined. The structure of prtA is similar t o that of the A. oryzae Alp-encoding gene. The prtA gene is composed o f four exons which are separated by three introns of 59, 57 and 54 nt. The deduced amino acid sequence of the prtA product shows a high degr ee of similarity to proteases from A. oryzae, A. fumigatus and A. flav us. Southern blot analysis suggests that only one copy of this gene is found in the genome of A. nidulans. The extracellular proteases of A. nidulans are regulated by nitrogen, carbon and sulfur metabolite repr ession. The prtA RNA levels were analysed under different nutrient con ditions. No prtA transcript was detected in mycelium grown in medium c ontaining glucose, NH4+ and sulfate. However, prtA transcript levels w ere high in mycelia transferred to medium lacking a nitrogen, carbon o r sulfur source.