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Identification and sequencing of the Escherichia coli cet gene which codes for an inner membrane protein, mutation of which causes tolerance to colicin E2
Author(s) -
Drury L. S.,
Buxton R. S.
Publication year - 1988
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1988.tb00012.x
Subject(s) - biology , regulon , colicin , gene , open reading frame , operon , mutant , genetics , microbiology and biotechnology , escherichia coli , gene product , gene expression , transmembrane protein , peptide sequence , receptor
Summary Dominant mutations of the cet gene of Escherichia coli result in tolerance to colicin E2 and increased amounts of an inner membrane protein with an M r of 42 000. We have cloned the cet + gene and sequenced its DNA, revealing that the gene product, coded by the longest open‐reading frame, has an M r of 49772, with five predicted transmembrane structures towards its carboxy terminus and one at its amino terminus. We have demonstrated that the cet locus does in fact code for the inner membrane protein that is present in increased amounts in cet mutants, and we have shown that this increased amount of Cet protein is the result of enhanced transcription. The cet gene is shown to be in the same operon as the phoM gene, which is required in a phoR background for expression of the structural gene for alkaline phosphatase, phoA. Although the Cet protein is not required for phoA expression, our experiments suggest that the Cet protein has an enhancing effect on the transcription of phoA. No effect of phosphate concentration on cet or phoM gene expression could be found and thus their primary function may not be connected to the phosphate regulon.