A secondary promoter for elongation factor Tu synthesis in the str ribosomal protein operon of Escherichia coli

✍ Scribed by Zengel, Janice M. ;Lindahl, Lasse

• Publisher: Springer
• Year: 1982
• Tongue: English
• Weight: 646 KB
• Volume: 185
• Category: Article
• ISSN: 0026-8925
• DOI: 10.1007/bf00334145

✦ Synopsis

The str operon of Escherichia coli contains genes for ribosomal proteins S12 and S7 and for elongation factors EF-G and EF-Tu (Jaskunas et al. 1975). We have subcloned various segments of DNA from this operon onto multicopy plasmids. We found that cells carrying a recombinant plasmid which lacks the major promoter for the str operon but contains the 5' portion of the EF-Tu gene synthesize a novel protein which we have identified as a truncated EF-Tu molecule. Moreover, cells carrying plasmids with an intact EF-Tu gene synthesize the elongation factor at a 3- to 5-fold higher rate than haploid cells. Thus the EF-Tu gene can be expressed in the absence of the major promoter for the str operon. This expression is not due to read-through from plasmid promoters, but it is dependent on the presence of the distal portion of the EF-G gene on the plasmids. These results indicate that there is a secondary promoter for EF-Tu expression, apparently located within the structural gene for elongation factor EF-G.