Absence of the outer membrane phospholipase A suppresses the temperature-sensitive phenotype of Escherichia coli degP mutants and induces the Cpx and sigma(E) extracytoplasmic stress responses.
DegP is a periplasmic protease that is a member of both the sigma(E) and Cpx extracytoplasmic stress regulons of Escherichia coli and is essential for viability at temperatures above 42 degrees C. [U-(14)C]acetate labeling experiments demonstrated that phospholipids were degraded in degP mutants at elevated temperatures. In addition, chloramphenicol acetyltransferase, beta-lactamase, and beta-galactosidase assays as well as sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis indicated that large amounts of cellular proteins are released from degP cells at the nonpermissive temperature. A mutation in pldA, which encodes outer membrane phospholipase A (OMPLA), was found to rescue degP cells from the temperature-sensitive phenotype. pldA degP mutants had a normal plating efficiency at 42 degrees C, displayed increased viability at 44 degrees C, showed no degradation of phospholipids, and released far lower amounts of cellular protein to culture supernatants. degP and pldA degP mutants containing chromosomal lacZ fusions to Cpx and sigma(E) regulon promoters indicated that both regulons were activated in the pldA mutants. The overexpression of the envelope lipoprotein, NlpE, which induces the Cpx regulon, was also found to suppress the temperature-sensitive phenotype of degP mutants but did not prevent the degradation of phospholipids. These results suggest that the absence of OMPLA corrects the degP temperature-sensitive phenotype by inducing the Cpx and sigma(E) regulons rather than by inactivating the phospholipase per se.
Langen
G R
GR
Department of Biology, University of Regina, Regina, Saskatchewan, Canada S4S 0A2.
Harper
J R
JR
Silhavy
T J
TJ
Howard
S P
SP
D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins; D018869:Heat-Shock Response; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D033903:Periplasmic Proteins; D010741:Phospholipases A / Q000235:genetics* / Q000378:metabolism; D054466:Phospholipases A1; D010743:Phospholipids / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D012697:Serine Endopeptidases / Q000235:genetics* / Q000378:metabolism; D012808:Sigma Factor / Q000378:metabolism; D015398:Signal Transduction; D013696:Temperature; D014157:Transcription Factors / Q000378:metabolism
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D008074:Lipoproteins; C095021:NlpE protein, E coli; D033903:Periplasmic Proteins; D010743:Phospholipids; D012808:Sigma Factor; D014157:Transcription Factors; C063202:sporulation-specific sigma factors; C085504:CpxR protein, Bacteria; D011494:Protein Kinases; C490475:CpxA protein, E coli; C092472:CpxA protein, bacteria; D010741:Phospholipases A; D054466:Phospholipases A1; C412876:outer membrane phospholipase A; C061682:DegP protease; D012697:Serine Endopeptidases