Department of Radiation Biology, University of Rochester School of Medicine, Rochester, New York 14642.
Genetics. 1979 Sep;93(1):51-65. doi: 10.1093/genetics/93.1.51.
Normal strains of Saccharomyces cerevisiae do not use alpha-aminoadipate as a principal nitrogen source. However, alpha-aminoadipate is utilized as a nitrogen source by lys2 and lys5 strains having complete or partial deficiencies of alpha-aminoadipate reductase and, to a limited extent, by heterozygous lys2/+ strains. Lys2 mutants were conveniently selected on media containing alpha-aminoadipate as a nitrogen source, lysine, and other supplements to furnish other possible auxotrophic requirements. The lys2 mutations were obtained in a variety of laboratory strains containing other markers, including other lysine mutations. In addition to the predominant class of lys2 mutants, low frequencies of lys5 mutants and mutants not having any obvious lysine requirement were recovered on alpha-aminoadipate medium. The mutants not requiring lysine appeared to have mutations at the lys2 locus that caused partial deficiencies of alpha-aminoadipate reductase. Such partial deficiencies are believed to be sufficiently permissive to allow lysine biosynthesis, but sufficiently restrictive to allow for the utilization of alpha-aminoadipate. Although it is unknown why partial or complete deficiencies of alpha-aminoadipate reductase cause utilization of alpha-aminoadipate as a principal nitrogen source, the use of alpha-aminoadipate medium has considerable utility as a selective medium for lys2 and lys5 mutants.
正常的酿酒酵母菌株不以α-氨基己二酸作为主要氮源。然而，lys2 和 lys5 菌株在完全或部分缺乏α-氨基己二酸还原酶的情况下，以及在一定程度上在杂合 lys2/+ 菌株中，将α-氨基己二酸用作氮源。lys2 突变体可以方便地在含有α-氨基己二酸作为氮源、赖氨酸和其他补充物的培养基上进行选择，以提供其他可能的营养缺陷需求。lys2 突变是在含有其他标记物的各种实验室菌株中获得的，包括其他赖氨酸突变。除了主要的 lys2 突变体外，在含有α-氨基己二酸的培养基上还回收了低频率的 lys5 突变体和没有明显赖氨酸需求的突变体。不需要赖氨酸的突变体似乎在 lys2 基因座上发生了突变，导致α-氨基己二酸还原酶的部分缺陷。这种部分缺陷被认为足够宽容，可以允许赖氨酸的生物合成，但又足够严格，可以允许α-氨基己二酸的利用。虽然不知道为什么α-氨基己二酸还原酶的部分或完全缺陷会导致α-氨基己二酸作为主要氮源的利用，但α-氨基己二酸培养基作为 lys2 和 lys5 突变体的选择性培养基具有相当大的用途。
