Cheney R W, Kredich N M
J Bacteriol. 1975 Dec;124(3):1273-81. doi: 10.1128/jb.124.3.1273-1281.1975.
A genetic map of the cysB region of the Salmonella typhimurium chromosome was constructed using bacteriophage P22-mediated transduction. Strains bearing delta (supX cysB) mutations were employed to divide this regulatory locus into 12 segments containing a total of 39 single-site mutations. Twenty-five of these single-site mutations were further ordered by reciprocal three-point crosses. The results do not support the concept of multiple cistrons at cysB and suggest that the abortive transductants previously observed in crosses between certain cysB mutants were due to intracistronic complementation. The prototrophic cys-1352 mutation, which causes the constitutive expression of the cysteine biosynthetic enzymes, was found to lie within the cysB region itself. It is bracketed by mutations, which lead to an inability to derepress for these enzymes and result in auxotrophy for cysteine.
利用噬菌体P22介导的转导构建了鼠伤寒沙门氏菌染色体cysB区域的遗传图谱。携带δ（supX cysB）突变的菌株被用于将这个调控位点划分为12个区段，共包含39个单点突变。通过相互三点杂交进一步确定了其中25个单点突变的顺序。结果不支持cysB存在多个顺反子的概念，并表明先前在某些cysB突变体杂交中观察到的流产转导子是由于顺反子内互补所致。导致半胱氨酸生物合成酶组成型表达的原养型cys-1352突变被发现位于cysB区域本身。它被一些突变包围，这些突变导致这些酶无法去阻遏，并导致半胱氨酸营养缺陷。
