Katz M E, Flynn P K, vanKuyk P A, Cheetham B F
Department of Molecular and Cellular Biology, University of New England, Armidale, N.S.W., Australia.
Mol Gen Genet. 1996 Apr 10;250(6):715-24. doi: 10.1007/BF02172983.
The extracellular proteases of Aspergillus nidulans are known to be regulated by carbon, nitrogen and sulphur metabolite repression. In this study, a mutant with reduced levels of extracellular protease was isolated by screening for loss of halo production on milk plates. Genetic analysis of the mutant showed that it contains a single, recessive mutation, in a gene which we have designated xprE, located on chromosome VI. The xprE1 mutation affected the production of extracellular proteases in response to carbon, nitrogen and, to a lesser extent, sulphur limitation. Three reversion mutations, xprF1, xprF2 and xprG1, which suppress xprE1, were characterised. Both xprF and xprG map to chromosome VII but the two genes are unlinked. The xprF1, xprF2 and xprG1 mutants showed high levels of milk-clearing activity on medium containing milk as a carbon source but reduced growth on a number of nitrogen sources. Evidence is presented that the xprE1 and xprG1 mutations alter expression of more than one protease and affect levels of alkaline protease gene mRNA.
已知构巢曲霉的胞外蛋白酶受碳、氮和硫代谢物阻遏调控。在本研究中，通过筛选在牛奶平板上晕圈产生缺失的菌株，分离出一株胞外蛋白酶水平降低的突变体。对该突变体的遗传分析表明，它在位于第六条染色体上的一个我们命名为xprE的基因中含有一个单一的隐性突变。xprE1突变影响胞外蛋白酶在碳、氮以及在较小程度上硫限制条件下的产生。对三个抑制xprE1的回复突变xprF1、xprF2和xprG1进行了表征。xprF和xprG都定位在第七条染色体上，但这两个基因不连锁。xprF1、xprF2和xprG1突变体在以牛奶为碳源的培养基上表现出高水平的牛奶分解活性，但在多种氮源上生长受到抑制。有证据表明，xprE1和xprG1突变改变了不止一种蛋白酶的表达，并影响碱性蛋白酶基因mRNA的水平。
