Charron M J, Michels C A
Department of Biology, Queens College, Flushing, New York.
Genetics. 1988 Sep;120(1):83-93. doi: 10.1093/genetics/120.1.83.
In order for a yeast strain to ferment maltose it must contain any one of the five dominant MAL loci. Each dominant MAL locus thus far analyzed contains three genes: GENE 1, encoding maltose permease, GENE 2 encoding maltase and GENE 3 encoding a positive trans-acting regulatory protein. In addition to these dominant MAL loci, several naturally occurring, partially functional alleles of MAL1 and MAL3 have been identified. Here, we present genetic and molecular analysis of the three partially functional alleles of MAL1: the MAL1p allele which can express only the MAL activator; the MAL1 g allele which can express both a maltose permease and maltase; and the mal1(0) allele which can express only maltase. Based on our results, we propose that the MAL1p, MAL1g and mal1(0) alleles evolved from the dominant MAL1 locus by a series of rearrangements and/or deletions of this yeast telomere-associated locus as well as by other mutagenic processes of gene inactivation. One surprising finding is that the MAL1g-encoded maltose permease exhibits little sequence homology to the MAL1-encoded maltose permease though they appear to be functionally homologous.
为了使酵母菌株能够发酵麦芽糖，它必须含有五个显性MAL基因座中的任何一个。到目前为止分析的每个显性MAL基因座都包含三个基因：基因1，编码麦芽糖通透酶；基因2，编码麦芽糖酶；基因3，编码一种正向反式作用调节蛋白。除了这些显性MAL基因座外，还鉴定出了几个天然存在的、部分功能的MAL1和MAL3等位基因。在这里，我们对MAL1的三个部分功能等位基因进行了遗传和分子分析：MAL1p等位基因，只能表达MAL激活剂；MAL1g等位基因，能表达麦芽糖通透酶和麦芽糖酶；mal1(0)等位基因，只能表达麦芽糖酶。根据我们的结果，我们提出MAL1p、MAL1g和mal1(0)等位基因是通过该酵母端粒相关基因座的一系列重排和/或缺失以及其他基因失活的诱变过程从显性MAL1基因座进化而来的。一个令人惊讶的发现是，MAL1g编码的麦芽糖通透酶与MAL1编码的麦芽糖通透酶虽然功能上似乎同源，但序列同源性很低。
