Phosphotransferase-mediated regulation of carbohydrate utilisation in Escherichia coli K12: identification of the products of genes on the specialised transducing phages lambda iex (crr) and lambda gsr (tgs).

The expression of genes adjacent to ptsI was investigated using a series of specialised transducing phages carrying different, overlapping, segments of the cysA-gsr-ptsI-ptsH- iex - cysZ -lig region of the genome of Escherichia coli. The polypeptides were synthesised following the infection of u.v.-irradiated lysogenic and non-lysogenic uvrA recA hosts or a uvrA recA host carrying the lambda cI+ plasmid pKB280 . The polypeptides were identified by SDS-polyacrylamide gel electrophoresis and fluorography. The gsr gene product had a mol. wt. of 23 000. The product of the iex gene was tentatively identified as a protein of mol. wt. of either 33 000 or 21 000. Hpr, the product of the gene ptsH, had a mol. wt. of 9000. The gsr gene appeared to be expressed at a higher level in a non-immune host, which suggests that it was transcribed from lambda promoters. A new lambda host strain, suitable for the detection of small polypeptides (mol. wt. less than 30 000) is described.