Gunsalus R P, Yanofsky C
Proc Natl Acad Sci U S A. 1980 Dec;77(12):7117-21. doi: 10.1073/pnas.77.12.7117.
The nucleotide sequence of trpR of Escherichia coli was determined. This gene codes for a polypeptide (Mr 12,356) that is 108 amino acid residues in length. NH2-terminal, COOH-terminal, and total amino acid analyses of purified aporepressor agree with the deduced amino acid sequence and establish the translation start and stop codons of the structural gene. The transcription start site for trpR mRNA synthesis in vitro was shown to be 56 base pairs prior to the translation start site. The nucleotide sequence on either side of the transcription start site is homologous to the trp operon operator. Purified trp aporepressor, when activated by L-tryptophan, protects restriction sites in this region, the presumed trpR operator, from cleavage by the respective restriction endonucleases. Bound RNA polymerase protects the same restriction sites. These findings and the additional observation that trp repressor inhibits transcription initiation in vitro establish that there is a functional overlap of operator and promoter sequences in the regulatory region of the trpR operon. These findings indicate that expression of trpR is autoregulatory.
测定了大肠杆菌色氨酸阻遏蛋白（trpR）的核苷酸序列。该基因编码一个长度为108个氨基酸残基的多肽（分子量12,356）。对纯化的无辅基阻遏蛋白进行的氨基末端、羧基末端及全氨基酸分析与推导的氨基酸序列相符，并确定了结构基因的翻译起始和终止密码子。体外trpR mRNA合成的转录起始位点显示在翻译起始位点之前56个碱基对处。转录起始位点两侧的核苷酸序列与色氨酸操纵子的操纵基因同源。纯化的色氨酸无辅基阻遏蛋白在被L-色氨酸激活后，可保护该区域（推测的trpR操纵基因）中的限制酶切位点不被相应的限制性内切酶切割。结合的RNA聚合酶也能保护相同的限制酶切位点。这些发现以及色氨酸阻遏蛋白在体外抑制转录起始的额外观察结果表明，在trpR操纵子的调控区域中，操纵基因和启动子序列存在功能重叠。这些发现表明trpR的表达是自动调节的。
