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|標題:||Expression of heat-shock genes groESL in Xanthomonas campestris is upregulated by CLP in an indirect manner||作者:||Chang, W.H.
|關鍵字:||transcription factor CLP;heat-shock genes;positive regulation;proteomic analysis;transcriptional fusion assay;Xanthomonas;transcription factor clp;phage phi-lf;agrobacterium-tumefaciens;stationary-phase;protein;dna;rpoh;sigma(32);bacteria;complex||Project:||Fems Microbiology Letters||期刊/報告no：:||Fems Microbiology Letters, Volume 243, Issue 2, Page(s) 365-372.||摘要:||
CLP is a homologue of cyclic AMP-receptor protein in Xanthomonas campestris. In this study, proteomic analysis and Western blotting showed that the clp mutant (TC820) of X campestris synthesizes less GroESL proteins than the parental P20H. The groESL upstream regions, nt -583 to -32 (552 bp) and nt -178 to -29 (150 bp) relative to the groESL initiation codon, were cloned for transcriptional fusion assays. The 150-bp region, bearing putative sigma(24)- and sigma(32)-binding sites and the CIRCE element all known to regulate groESL operon, expressed the same levels of beta-galactosidase (300 U/ml) in both strains, indicating that CLP is not involved in the expression from this region. At early exponential phase, the 552-bp region displayed extremely high levels of promoter activity, 11,000 U/ml in P20H versus 5000 U/ml in TC820. The enzyme levels were about 2000 U/ml at stationary phase in both strains, indicating high levels of expression when cells cease growing. These results suggest that the sequence responding to CLP regulation resides between nt -178 and -583. However, since this region has no CLP-binding site and showed no binding to CLP in gel retardation assay, CLP is likely acting indirectly. This communication appears to be the first description of the positive regulation of a bacterial heat-shock operon by a CRP homologue. (C) 2004 Published by Elsevier B.V. on behalf of the Federation of European Microbiological Societies.
|Appears in Collections:||分子生物學研究所|
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