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Response of Escherichia coli cell membranes to induction of λ c 1857 prophage by heat shock
Author(s) -
Kucharczyk K.,
Laskowska E.,
Taylor A.
Publication year - 1991
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1991.tb01853.x
Subject(s) - prophage , biology , escherichia coli , heat shock , microbiology and biotechnology , shock (circulatory) , membrane , heat shock protein , genetics , gene , bacteriophage , medicine
Summary Heat shock induces protein aggregation in Escherichia coli and E. coli (λ c 1857). The aggregates (S fraction) appear 15 min post‐induction and are separable from membranes by sucrose density‐gradient centrifugation. The S fraction quickly disappears in wild type strains but persists in rpoH mutant with concomitant quick inner membrane destruction. We propose that: (1) the disappearance of the S fraction reflects a rpoH ‐dependent processing, (2) the membrane destruction explains the lethality of the rpoH mutation at elevated temperatures; and (3) the protection of the inner membrane integrity is an important physiological function of the heat‐shock response. We assume that the S fraction of aggregated proteins represents the signal inducing the heat‐shock response. The prophage thermo‐induction results in an increase (35 min post‐induction) in the A fraction resembling that of the adhesion zones of the membranes. This fraction is greater than the corresponding fraction from uninduced cells. The increase is mediated by the λ late genes, since it is absent in the induced E.coli (λ c 1857 Oam21). Since heat shock is widely used for induction of the λ promoters in expression vectors it is possible that the formation of the protein aggregates (though transient in WT strains) and/or the fragility of membranes in rpoH mutants may be the cause of poor expression of cloned genes or may lead to mistaken localization of their expression products.