Balbinder E, Blume A J, Weber A, Tamaki H
J Bacteriol. 1968 Jun;95(6):2217-29. doi: 10.1128/jb.95.6.2217-2229.1968.
Polar mutations in trpA, the first structural gene of the tryptophan operon of Salmonella typhimurium, have an uncoordinate effect on the expression of the distal genes, with trpB, the second gene, being more drastically affected than the last three. A number of these polar mutant strains grow very poorly on anthranilic acid-supplemented minimal medium. By selecting for more rapid growth in the presence of anthranilic acid, secondary mutant clones showing a correction of the polar effect were isolated. A few of these were analyzed and shown to contain deletions of various segments of the trpA gene. Ten randomly isolated deletion mutants missing various segments of the trp operon were analyzed for possible pleiotropic effects. Five of them showed a pleiotropic effect of some sort and five did not. Of those showing pleiotropic effects, one had lost the promotor-like elements necessary to initiate expression of the operon, three showed possible antipolar effects, and one showed both polar and antipolar effects simultaneously.
鼠伤寒沙门氏菌色氨酸操纵子的第一个结构基因trpA中的极性突变，对远端基因的表达有不协调的影响，其中第二个基因trpB受到的影响比最后三个基因更严重。许多这些极性突变菌株在补充邻氨基苯甲酸的基本培养基上生长非常差。通过选择在邻氨基苯甲酸存在下生长更快的菌株，分离出了显示极性效应得到校正的二级突变克隆。对其中一些进行了分析，结果表明它们含有trpA基因不同片段的缺失。分析了十个随机分离的缺失trp操纵子不同片段的缺失突变体，以研究可能的多效性效应。其中五个显示出某种多效性效应，五个则没有。在显示多效性效应的突变体中，一个失去了启动操纵子表达所需的类似启动子的元件，三个显示出可能的反极性效应，一个同时显示出极性和反极性效应。
