Philley M L, Staben C
T. H. Morgan School of Biological Sciences, University of Kentucky, Lexington 40506-0225.
Genetics. 1994 Jul;137(3):715-22. doi: 10.1093/genetics/137.3.715.
The Neurospora crassa mt a-1 gene, encoding the MT a-1 polypeptide, determines a mating type properties: sexual compatibility and vegetative incompatibility with A mating type. We characterized in vivo and in vitro functions of the MT a-1 polypeptide and specific mutant derivatives. MT a-1 polypeptide produced in Escherichia coli bound to specific DNA sequences whose core was 5'-CTTTG-3'. DNA binding was a function of the MT a-1 HMG box domain (a DNA binding motif found in high mobility group proteins and a diverse set of regulatory proteins). Mutation within the HMG box eliminated DNA binding in vitro and eliminated mating in vivo, but did not interfere with vegetative incompatibility function in vivo. Conversely, deletion of amino acids 216-220 of MT a-1 eliminated vegetative incompatibility, but did not affect mating or DNA binding. Deletion of the carboxyl terminal half of MT a-1 eliminated both mating and vegetative incompatibility in vivo, but not DNA binding in vitro. These results suggest that mating depends upon the ability of MT a-1 polypeptide to bind to, and presumably to regulate the activity of, specific DNA sequences. However, the separation of vegetative incompatibility from both mating and DNA binding indicates that vegetative incompatibility functions by a biochemically distinct mechanism.
粗糙脉孢菌的mt a-1基因编码MT a-1多肽，决定了一种交配型特性：与A交配型的有性亲和性和营养体不亲和性。我们对MT a-1多肽及其特定突变衍生物的体内和体外功能进行了表征。在大肠杆菌中产生的MT a-1多肽与核心为5'-CTTTG-3'的特定DNA序列结合。DNA结合是MT a-1 HMG盒结构域（在高迁移率族蛋白和多种调节蛋白中发现的一种DNA结合基序）的功能。HMG盒内的突变消除了体外DNA结合并消除了体内交配，但不干扰体内营养体不亲和性功能。相反，MT a-1的216-220位氨基酸缺失消除了营养体不亲和性，但不影响交配或DNA结合。MT a-1羧基末端一半的缺失消除了体内交配和营养体不亲和性，但不影响体外DNA结合。这些结果表明，交配取决于MT a-1多肽与特定DNA序列结合并可能调节其活性的能力。然而，营养体不亲和性与交配和DNA结合的分离表明，营养体不亲和性通过一种生化上不同的机制发挥作用。
