Matsui K, Miwa K, Sano K
Central Research Laboratories, Ajinomoto Co. Inc., Kawasaki, Japan.
J Bacteriol. 1987 Nov;169(11):5330-2. doi: 10.1128/jb.169.11.5330-5332.1987.
A 5-fluorotryptophan-resistant mutant, termed 1041, was isolated from Brevibacterium lactofermentum AJ12036. The anthranilate synthase of 1041 was insensitive to feedback inhibition by tryptophan, and the specific activities of the anthranilate synthase and anthranilate phosphoribosyltransferase of 1041 were 29- and 23-fold higher than those in parental strain AJ12036, respectively. A single-base change (adenine to cytosine) that resulted in a Ser-to-Arg substitution was found in the trpE structural gene of 1041. This substitution was identified as the cause of the desensitization to feedback inhibition by tryptophan of anthranilate synthase in 1041. Another substitution (guanine to adenine) was found at a position in which a mutation would destabilize the rho-independent terminator structure within the putative attenuator. The enhanced synthesis of tryptophan enzymes in 1041 could be caused by this substitution in the attenuator.
从乳酸发酵短杆菌AJ12036中分离出一株对5-氟色氨酸具有抗性的突变体，命名为1041。1041的邻氨基苯甲酸合酶对色氨酸的反馈抑制不敏感，其邻氨基苯甲酸合酶和邻氨基苯甲酸磷酸核糖转移酶的比活性分别比亲本菌株AJ12036高29倍和23倍。在1041的trpE结构基因中发现了一个单碱基变化（腺嘌呤到胞嘧啶），导致丝氨酸被精氨酸取代。该取代被确定为1041中邻氨基苯甲酸合酶对色氨酸反馈抑制脱敏的原因。在一个突变会破坏假定衰减子内的ρ非依赖性终止子结构的位置发现了另一个取代（鸟嘌呤到腺嘌呤）。1041中色氨酸酶合成的增强可能是由衰减子中的这种取代引起的。
