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Stress induction of the Bacillus subtilis clpP gene encoding a homologue of the proteolytic component of the Clp protease and the involvement of ClpP and ClpX in stress tolerance
Author(s) -
Gerth Ulf,
Krüger Elke,
Derré Isabelle,
Msadek Tarek,
Hecker Michael
Publication year - 1998
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 - 10.1046/j.1365-2958.1998.00840.x
Subject(s) - biology , bacillus subtilis , protease , gene , component (thermodynamics) , genetics , microbiology and biotechnology , biochemistry , enzyme , bacteria , physics , thermodynamics
The Bacillus subtilis clpP gene, encoding the proteolytic component of the Clp or Ti protease, was cloned and sequenced. The amount of clpP ‐specific mRNA increased after heat shock, salt and ethanol stress, as well as after treatment with puromycin. Two transcriptional start sites upstream of the clpP structural gene were identified, preceded by sequences resembling the consensus sequences of promoters recognized by σ A andσ B transcriptional factors of the B . subtilis RNA polymerase respectively. Transcription initiation occurred predominantly at the putative σ A ‐dependent promoter in exponentially growing cells and was induced under stress conditions. After exposure to stress, initiation of transcription also increased at the σ B ‐dependent promoter, but to a lesser extent, indicating that clpP belongs to a double promoter‐controlled subgroup of class III general stress genes in B . subtilis . In a sigB mutant strain, clpP remained heat and stress inducible at the σ A ‐dependent promoter. BgaB–reporter gene fusions, carrying either the σ A ‐ or the σ B ‐dependent promoter, showed a higher bgaB induction at the σ A ‐dependent promoter, whereas a significantly lower level of induction was measured at the σ B ‐dependent promoter. The σ A ‐dependent promoter appeared to be crucial for the heat‐inducible transcription of clpP . A CIRCE (controlling inverted repeat of chaperone expression) element, the characteristic regulation target of class I heat shock genes such as dnaK and groESL , was not found between the transcriptional and translational start sites. Mutants lacking either the proteolytic component ClpP or the regulatory ATPase component ClpX were phenotypically distinct from the wild type. Both mutants produced chains of elongated cells and exhibited severely impaired growth under stress conditions and starvation. Comparison of two‐dimensional protein gels from wild‐type cells with those from clpP and clpX mutant cells revealed several changes in the protein pattern. Several proteins, such as GroEL, PpiB, PykA, SucD, YhfP, YqkF, YugJ and YvyD, which were found preferentially in higher amounts in both clpP and clpX mutants, might be potential substrates for the ClpXP protease.