PMID:15951035
| Citation |
Nishiyama, K and Tokuda, H (2005) Genes coding for SecG and Leu2-tRNA form an operon to give an unusual RNA comprising mRNA and a tRNA precursor. Biochim. Biophys. Acta 1729:166-73 |
|---|---|
| Abstract |
The secG gene encoding the SecG subunit of the SecYEG translocon and the leuU gene encoding Leu2-tRNA are very closely located on the Escherichia coli chromosome. A secG-leuU disruptant was not viable unless secG-leuU was induced from a plasmid, indicating that leuU is an essential gene since secG is dispensable at 37 degrees C. A mutant strain in which the promoter region for secG was replaced with cat revealed the same phenotype as the secG-leuU disruptant, indicating that leuU was expressed from the secG promoter. When the secG-leuU locus was placed on a high copy plasmid, an RNA comprising both mRNA for SecG and a precursor for Leu2-tRNA was detected on a Northern blot. Moreover, a secG-leuU transcript was amplified by RT-PCR using the total RNA fraction prepared from wild type E. coli cells but not from the secG-leuU and the secG promoter disruptants, indicating that secG-leuU forms an operon. Thus, the expression of Leu2-tRNA requires expression of the upstream secG gene. The gene structure of secG-leuU was conserved among Gram-negative bacteria, although the sequences separating the two genes were quite diverse. The physiological significance of this unusual gene organization is discussed. |
| Links |
PubMed Online version:10.1016/j.bbaexp.2005.05.003 |
| Keywords |
Amino Acid Sequence; Base Sequence; Blotting, Northern; Escherichia coli/genetics; Escherichia coli Proteins/genetics; Gene Expression Regulation, Bacterial; Membrane Proteins/genetics; Molecular Sequence Data; Operon; Promoter Regions, Genetic/genetics; RNA Precursors/genetics; RNA Precursors/metabolism; RNA Processing, Post-Transcriptional; RNA, Bacterial/genetics; RNA, Transfer, Leu/genetics; Transcription, Genetic |
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