Multiple deletions reveal the essentiality of the DedA membrane protein family in Escherichia coli.

The DedA family is a highly conserved, ancient family of membrane proteins with representatives in most sequenced genomes. A characteristic of prokaryotic DedA family genes is extensive gene duplication, with most bacterial genomes carrying two or more homologues. The Escherichia coli genome carries eight DedA genes, each individually nonessential. We previously described an E. coli mutant (BC202; ΔyghB : : kan(R), ΔyqjA : : tet(R)) with in-frame deletions of two DedA genes encoding proteins with 61 % amino acid identity. BC202 fails to complete cell division or grow at elevated temperatures. Here, we report that restoration of normal growth and cell division of BC202 is possible by overexpression of a subset of the eight E. coli DedA genes (yabI, yohD, yqjA and yghB) but not others (dedA, ydjX, ydjZ and yqaA), suggesting the existence of two functional groups within the family. We have constructed individual E. coli strains in which all eight DedA genes are deleted in a nonpolar manner, and growth is supported by a single DedA family gene under control of an inducible promoter. Strain BAL801 (with growth supported by cloned dedA) and BAL802 (with growth supported by cloned yqjA) exhibit slow growth that is absolutely dependent upon the presence of the arabinose inducer. Growth in the presence of glucose results in cell death. These results indicate that while not individually essential, the E. coli DedA family proteins are collectively essential. These observations suggest important functions for the E. coli DedA protein family.