PMID:6436819

Citation	Goff, SA, Casson, LP and Goldberg, AL (1984) Heat shock regulatory gene htpR influences rates of protein degradation and expression of the lon gene in Escherichia coli. Proc. Natl. Acad. Sci. U.S.A. 81:6647-51
Abstract	Upon a shift to high temperature, Escherichia coli increase their rate of protein degradation and also the expression of a set of "heat shock" genes. Nonsense mutants of htpR (also called hin), suppressed by a temperature-sensitive suppressor, show lower expression of heat shock genes at 30 degrees C and fail to respond to a shift to 42 degrees C. These mutants were found to have a lower capacity to degrade abnormal or incomplete proteins than that of wild-type cells. This reduction in proteolysis equals or exceeds that in lon mutants, which encode a defective ATP-dependent protease, protease La, and is particularly large in htpR lon double mutants. The activity of protease La was higher in wild-type cells than in htpR mutants grown at 30 degrees C and increased upon shift to 42 degrees C only in the wild type. To determine whether htpR influences transcription of the lon gene, a lon-lacZ operon fusion was utilized. Introduction of the htpR mutation reduced transcription from the lon promoter at 30 degrees C and 37 degrees C. This defect was corrected by a plasmid (pFN97) carrying the wild-type htpR allele. Induction of the heat shock response with ethanol had little or no effect in htpR mutants but stimulated lon transcription 2-3 fold in wild-type cells and htpR cells carrying pFN97. Thus, lon appears to be a heat shock gene, and increased synthesis of protease La under stressful conditions may help to prevent the accumulation of damaged cellular protein.
Links	PubMed PMC391987
Keywords	ATP-Dependent Proteases; Adenosine Triphosphate/pharmacology; Bacterial Proteins/metabolism; DNA, Recombinant; Endopeptidases/metabolism; Escherichia coli/genetics; Escherichia coli/metabolism; Escherichia coli Proteins; Genes, Bacterial; Genes, Regulator; Heat-Shock Proteins/genetics; Hot Temperature; Lac Operon; Mutation; Operon; Phenotype; Protease La; Serine Endopeptidases; Transcription, Genetic; beta-Galactosidase/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ECOLI:LON		GO:0009408: response to heat	ECO:0000270:		P		Table 1. shows upregulation of Lon in response to heat exposure (42C)	complete
ECOLI:LON		GO:0009411: response to UV	ECO:0000315:		P		Table 3. Increased UV sensitivity in mutant lon	complete
ECOLI:LON		GO:0006508: proteolysis	ECO:0000315:		P		Fig. 1 and 2 show decreased proteolytic activity in the mutant phenotype	complete
ECOLI:LON		GO:0045471: response to ethanol	ECO:0000270:		P		Table 1. shows enhanced Lon expression in the presence of ethanol (4%)	complete

References

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