title: A secondary promoter for elongation factor Tu synthesis in the str ribosomal protein operon of Escherichia coli.
abstract: 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.
mesh_terms: D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D004274:DNA, Recombinant / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics*; D005796:Genes; D009154:Mutation; D009876:Operon; D010444:Peptide Elongation Factor Tu; D010445:Peptide Elongation Factors / Q000235:genetics*; D010446:Peptide Fragments / Q000032:analysis; D010957:Plasmids; D012269:Ribosomal Proteins / Q000235:genetics*
chemical_list: D004274:DNA, Recombinant; D010445:Peptide Elongation Factors; D010446:Peptide Fragments; D012269:Ribosomal Proteins; D004262:DNA Restriction Enzymes; D010444:Peptide Elongation Factor Tu