Studies on the function and regulation of heat shock proteins in Escherichia coli
The heat shock proteins of Escherichia coli are a set of 17 protein whose synthesis is transiently induced following a rapid increase in growth temperature. The author has found that at least one general function of heat shock proteins is to contribute to the ability of the cell to degrade abnormal polypeptides. Mutations in the dnaK, dnaJ, grpE, and groEL heat shock genes result in defects in the degradation of abnormal proteins. In addition, overproduction of heat shock proteins results in enhanced rates of abnormal protein degradation. Expression of heat shock genes is dependent upon the function of the rpoH gene product, {sigma}{sup 32}, which directs RNA polymerase to initiate transcription at heat shock promoters. He has found that {sigma}{sup 32} directly regulates heat shock gene expression. Rapid changes in the intracellular concentration of {sigma}{sup 32} are sufficient to explain the transient induction of heat shock proteins following temperature upshift. Changes in the concentration of {sigma}{sup 32} occur as the result of regulation of both the synthesis and stability of {sigma}{sup 32}. Analysis of fusions between rpoH and lacZ suggests that synthesis of {sigma}{sup 32} is regulated translationally. Changes, in the activity of {sigma}{sup 32} are also responsible for regulating heat shock gene expression. Transcription initiation at heat shock promoters is rapidly inhibited following temperature downshift, but the level of {sigma}{sup 32} decreases only slightly. In addition, induction of heat shock proteins following artificial overproduction of {sigma}{sup 32} is only transient, despite the fact that the level of {sigma}{sup 32} remains elevated.
- Research Organization:
- Wisconsin Univ., Madison, WI (USA)
- OSTI ID:
- 5657657
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ESCHERICHIA COLI
TEMPERATURE EFFECTS
POLYPEPTIDES
METABOLISM
PROTEINS
BIOSYNTHESIS
BIOLOGICAL FUNCTIONS
GENE MUTATIONS
GENE REGULATION
HEAT
TRANSCRIPTION
BACTERIA
ENERGY
MICROORGANISMS
MUTATIONS
ORGANIC COMPOUNDS
PEPTIDES
SYNTHESIS
560200* - Thermal Effects