DNA sequence analysis of the dye gene of Escherichia coli reveals amino acid homology between the dye and OmpR proteins.

Mutation of the dye gene of Escherichia coli results in sensitivity of dyes, envelope protein changes, loss of expression of alkaline phosphatase, and reduced transcription of sex factor F genes. We have determined the DNA sequence of a 1.4-kilobase pair fragment encompassing the dye gene. The coding sequence of dye was identified as an open reading frame coding for a protein of Mr 27,346. A sequence of 54 residues at the amino terminus was extremely acidic, with 12 aspartic plus glutamic acid residues and only 2 lysine plus arginine residues. A sequence of 19 adjacent residues near the center of the protein was identical, except for one mismatch, with a sequence in the OmpR protein, involved in controlling the amounts of the major outer membrane proteins OmpF and OmpC at the level of transcription. 28% of the Dye protein was homologous with OmpR. The positions of dye and ompR on the genetic map were indicative of a gene duplication. It seems likely, therefore, that the Dye and OmpR proteins are related, and Dye may thus be involved in the osmoregulation of envelope protein genes as well as being required for sex factor gene expression. The Dye protein itself, like OmpR, was shown not to be an envelope protein. A second open reading frame on the other DNA strand may use the same transcription termination site as dye.