title: Expression of heat shock protein D 48.5 of Escherichia coli is subject to modulation by catabolite repression.
abstract: The Escherichia coli heat shock regulon consists of approximately twenty polypeptides that are coordinately and transiently induced upon a temperature upshift under the control of an alternative sigma factor, designated sigma-32 or HtpR. Preliminary observations on one of the proteins of the heat shock response, protein D 48.5, suggested that its induction by sigma-32 during heat shock may be modulated by catabolite repression. In this study, a disk diffusion assay was used to screen the effect of several compounds on the expression of a lacZ fusion in the gene encoding protein D 48.5. This assay indicated that the expression of this protein was controlled, at least in part, by the catabolite repression response. A more indepth analysis of the expression of protein D 48.5 under both steady-state and heat shock conditions was conducted in both a wild type and cya crp background. This analysis revealed that in the cya crp background, the steady-state level of protein D 48.5 was elevated relative to the wildtype, but that the heat shock induction of the protein was reduced in magnitude relative to the wild type strain, suggesting a direct link between these two global responses. The lacZ fusion in the structural gene for protein D 48.5 should prove useful as a reporter mechanism to probe the physiology and regulation of the heat shock response.
authors.affiliation: Enteric Microbiology Branch, U.S. Naval Medical Research Unit No.3, Cairo, Egypt.
authors.forename: L F
authors.initials: LF
authors.lastname: Peruski
mesh_terms: D003001:Cloning, Molecular; D015180:Electrophoresis, Gel, Two-Dimensional; D004926:Escherichia coli / Q000235:genetics*; D005696:Galactosidases / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects / Q000235:genetics*; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics*; D007091:Image Processing, Computer-Assisted; D007763:Lac Operon; D012097:Repressor Proteins / Q000235:genetics*
chemical_list: D006360:Heat-Shock Proteins; D012097:Repressor Proteins; D005696:Galactosidases