Metabolic instability of Escherichia coli cyclopropane fatty acid synthase is due to RpoH-dependent proteolysis.
Cyclopropane fatty acids (CFAs) are generally synthesized as bacterial cultures enter stationary phase. In Escherichia coli, the onset of CFA synthesis results from increased transcription of cfa, the gene encoding CFA synthase. However, the increased level of CFA synthase activity is transient; the activity quickly declines to the basal level. We report that the loss of CFA activity is due to proteolytic degradation dependent on expression of the heat shock regulon. CFA synthase degradation is unaffected by mutations in the lon, clpP, and groEL genes or by depletion of the intracellular ATP pools. It seems likely that CFA synthase is the target of an unidentified energy-independent heat shock regulon protease. This seems to be the first example of heat shock-dependent degradation of a normal biosynthetic enzyme.
Chang
Y Y
YY
Department of Microbiology, University of Illinois, Urbana, Illinois 61801, USA.
Eichel
J
J
Cronan
J E
JE
D000251:Adenosine Triphosphatases / Q000235:genetics; D018834:Chaperonin 60 / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D049071:Endopeptidase Clp; D004795:Enzyme Stability; D004926:Escherichia coli / Q000201:enzymology*; D006360:Heat-Shock Proteins / Q000378:metabolism*; D008780:Methyltransferases / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D018085:Regulon / Q000235:genetics; D012697:Serine Endopeptidases / Q000235:genetics; D012808:Sigma Factor; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*
D018834:Chaperonin 60; D006360:Heat-Shock Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C069774:heat-shock sigma factor 32; D008780:Methyltransferases; C019964:cyclopropane synthetase; D012697:Serine Endopeptidases; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases