Isolation and characterization of Bacillus subtilis groE regulatory mutants: evidence for orf39 in the dnaK operon as a repressor gene in regulating the expression of both groE and dnaK.
AUTOR(ES)
Yuan, G
RESUMO
An inverted repeat sequence known as CIRCE (controlling inverted repeat of chaperone expression) in the Bacillus subtilis groE operon has been suggested to function as an operator. To identify the regulatory gene directly or indirectly involved in CIRCE-mediated heat-inducible groE expression, B. subtilis WBG2, carrying an integrated groE-bgaB transcription fusion in the amyE locus, was mutagenized. Dark blue colonies formed at 37 degrees C represent mutants which constitutively produce BgaB (a thermostable beta-galactosidase) at high levels. Seven mutants (WBG101 to WBG107) were selected for further characterization. They all overproduced BgaB, GroEL, and DnaK simultaneously at 37 degrees C. These mutants could be restored to normal by introducing a plasmid carrying a functional copy of orf39, the first gene in the B. subtilis dnaK operon. Genomic sequencing of these mutants demonstrated that they all carried a single mutation in orf39. These mutations can be divided into three groups: (i) Gly-307 to Asp, (ii) Ser-122 to Phe, and (iii) Gly-63 to Glu. By using a binary vector system in E. coli, production of ORF39 was found to negatively regulate the expression of groE-bgaB in a CIRCE-specific manner. Under the heat shock condition, the negative regulation mediated by ORF39 was abolished. Mobility shift of the CIRCE-containing probe was also observed with the crude extract prepared from the E. coli strain that overproduced ORF39. Therefore, ORF39 is the negative regulatory factor which regulates both groE and dnaK expression in B. subtilis. It is likely to function as a CIRCE-specific repressor.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=177496Documentos Relacionados
- Transcriptional organization and regulation of the dnaK and groE operons of Chlamydia trachomatis.
- The dnaK operon of Bacillus subtilis is heptacistronic.
- Isolation and sequence analysis of the Chlamydia pneumoniae GroE operon.
- Complete nucleotide sequence of the Bacillus subtilis dnaK gene.
- Expression and control of an operon from an intracellular symbiont which is homologous to the groE operon.