Gavini N, Davidson B E
Russell Grimwade School of Biochemistry, University of Melbourne, Parkvillé, Victoria, Australia.
J Biol Chem. 1990 Dec 15;265(35):21527-31.
Nucleotide sequence analysis and transposon 5 (Tn5) insertional mutagenesis indicate that the Escherichia coli gene pheR encodes tRNA(Phe) and not a repressor protein as previously reported. The coding region of pheR is identical to that of three other cloned tRNA(Phe) genes, pheU, pheV, and pheW. Multicopy plasmids carrying pheR, like those carrying pheU, pheV, or pheW, complement a temperature-sensitive lesion in the gene for the alpha-subunit of phenylalanyl-tRNA synthetase (pheS). The nucleotide sequences of the 5'-flanking DNA of pheR, pheU, and pheW are almost identical but are quite different from the same region of pheV. By comparison with pheV, which has two tandem promoters, pheR was found to have a single promoter. The expression of pheA (encoding chorismate mutase/prephenate dehydratase) in strains carrying the pheR374 allele was decreased to similar extents by multicopy plasmids containing either pheR or pheV. It is proposed that this decrease in pheA expression and the increase in expression of pheA previously reported for chromosomal pheR mutants are both mediated through the attenuation control mechanism that regulates pheA.
核苷酸序列分析和转座子5（Tn5）插入诱变表明，大肠杆菌基因pheR编码tRNA（Phe），而不是如先前报道的阻遏蛋白。pheR的编码区与其他三个克隆的tRNA（Phe）基因pheU、pheV和pheW的编码区相同。携带pheR的多拷贝质粒，与携带pheU、pheV或pheW的质粒一样，可弥补苯丙氨酰-tRNA合成酶（pheS）α亚基基因中的温度敏感损伤。pheR、pheU和pheW的5'侧翼DNA的核苷酸序列几乎相同，但与pheV的同一区域有很大差异。与具有两个串联启动子的pheV相比，发现pheR有一个单一启动子。携带pheR374等位基因的菌株中，含有pheR或pheV的多拷贝质粒使pheA（编码分支酸变位酶/预苯酸脱水酶）的表达降低到相似程度。有人提出，pheA表达的这种降低以及先前报道的染色体pheR突变体中pheA表达的增加，都是通过调节pheA的衰减控制机制介导的。
