Furano A V, Sullivan M
J Biol Chem. 1978 Dec 10;253(23):8351-4.
Recent work from several laboratories has established the following points about the synthesis of the polypeptide chain elongation factors Tu and G in Escherichia coli. (i) Elongation factor Tu is the product of duplicate, highly conserved genes, tufA and tufB, which are widely separate parts of the chromosome. (ii) The molar concentration of this factor is considerably higher than that of elongation factor G which is encoded by the fus gene. (iii) Although the tufA and fus genes are close together and can be co-transcribed in the direction from fus to tufA, the tufA gene product is synthesized at several times the rate of the fus gene product. In an attempt to understand what mechanism(s) could account for the differential expression of the tufA and fus genes, we sought to obtain more precise information on the physical relationship of these genes. By examining heteroduplexes between restriction endonuclease-generated fragments of DNA containing the tufA, fus, and tufB genes, we have demonstrated that the fus and tufA genes are intimately related physically in one of two possible arrangements. Either the NH2-terminal region of the tufA gene is contiguous with the COOH-terminal region of the fus gene or the beginning of the tufA gene overlaps part of the fus gene. These results mean that if the tufA gene is always co-transcribed with the fus gene, then some mechanism must allow the tufA portion of the transcript to be translated more often than the fus gene portion of the transcript.
