Characterization of six lipoproteins in the sigmaE regulon.
In Escherichia coli, sigma(E) regulon functions are required for envelope homeostasis during stress and are essential for viability under all growth conditions. The E. coli genome encodes approximately 100 lipoproteins, and 6 of these are regulated by sigma(E). Phenotypes associated with deletion of each of these lipoproteins are the subject of this report. One lipoprotein, YfiO, is essential for cellular viability. However, overexpression of this protein is not sufficient to alleviate the requirement of sigma(E) for viability, suggesting that the sigma(E) regulon provides more than one essential function. The remaining five lipoproteins in the sigma(E) regulon are nonessential; cells are viable even when all five are removed simultaneously. Deletion of three nonessential lipoprotein genes (nlpB, yraP, ygfL) results in the exhibition of phenotypes that suggest they are important for maintenance of the integrity of the cell envelope. deltanlpB cells are selectively sensitive to rifampin; deltayraP cells are selectively sensitive to sodium dodecyl sulfate. Such selective sensitivity has not been previously reported. Both deltayraP and deltanlpB are synthetically lethal with surA::Cm, which encodes a periplasmic chaperone and PPIase, suggesting that NlpB and YraP play roles in a periplasmic folding pathway that functions in parallel with that of SurA. Finally, the deltayfgL mutant exhibits a broad range of envelope defects, including sensitivity to several membrane-impermeable agents, an altered outer membrane protein profile, synthetic lethality with both surA::Cm and deltafkpA::Cm strains, and sensitivity to a bactericidal permeability-increasing peptide. We suggest that this lipoprotein performs a very important but as-yet-unknown function in maintaining the integrity of the cell envelope.
Onufryk
Christina
C
Department of Biochemistry & Biophysics, University of California, San Francisco, California 94143, USA.
Crouch
Marie-Laure
ML
Fang
Ferric C
FC
Gross
Carol A
CA
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins; D002473:Cell Wall; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D029968:Escherichia coli Proteins; D008074:Lipoproteins / Q000235:genetics*; D008969:Molecular Sequence Data; D017510:Protein Folding; D018085:Regulon; D012293:Rifampin / Q000494:pharmacology; D012808:Sigma Factor / Q000235:genetics*; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D013501:Surface-Active Agents / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics*
D001425:Bacterial Outer Membrane Proteins; C513739:BamD protein, E coli; D004791:Enzyme Inhibitors; D029968:Escherichia coli Proteins; D008074:Lipoproteins; D012808:Sigma Factor; D013501:Surface-Active Agents; D014157:Transcription Factors; C063202:sporulation-specific sigma factors; D012967:Sodium Dodecyl Sulfate; D012293:Rifampin