Moralejo P, Egan S M, Hidalgo E, Aguilar J
Department of Biochemistry, School of Pharmacy, University of Barcelona, Spain.
J Bacteriol. 1993 Sep;175(17):5585-94. doi: 10.1128/jb.175.17.5585-5594.1993.
The sequencing of the EcoRI-HindIII fragment complementing mutations in the structural genes of the L-rhamnose regulon of Escherichia coli has permitted identification of the open reading frames corresponding to rhaB, rhaA, and rhaD. The deduced amino acid sequences gave a 425-amino-acid polypeptide corresponding to rhamnulose kinase for rhaB, a 400-amino-acid polypeptide corresponding to rhamnose isomerase for rhaA, and a 274-amino-acid polypeptide corresponding to rhamnulose-1-phosphate aldolase for rhaD. Transcriptional fusions of the three putative promoter regions to lacZ showed that only the rhaB leader region acted as a promoter, as indicated by the high beta-galactosidase activity induced by rhamnose, while no significant activity from the rhaA and rhaD constructions was detected. The rhaB transcription start site was mapped to -24 relative to the start of translation. Mutations in the catabolic genes were used to show that L-rhamnose may directly induce rhaBAD transcription.
对大肠杆菌L - 鼠李糖操纵子结构基因中互补突变的EcoRI - HindIII片段进行测序，使得对应于rhaB、rhaA和rhaD的开放阅读框得以鉴定。推导的氨基酸序列给出了对应于rhaB的鼠李糖ulose激酶的425个氨基酸的多肽、对应于rhaA的鼠李糖异构酶的400个氨基酸的多肽以及对应于rhaD的鼠李糖ulose - 1 - 磷酸醛缩酶的274个氨基酸的多肽。三个假定启动子区域与lacZ的转录融合表明，只有rhaB前导区域起启动子作用，如鼠李糖诱导的高β - 半乳糖苷酶活性所示，而未检测到来自rhaA和rhaD构建体的显著活性。rhaB转录起始位点相对于翻译起始点定位于 - 24。分解代谢基因中的突变用于表明L - 鼠李糖可能直接诱导rhaBAD转录。
