The Crl protein activates cryptic genes for curli formation and fibronectin binding in Escherichia coli HB101.
Curli are thin, coiled, temperature-regulated fibres on fibronectin-binding Escherichia coli. The subunit protein of curli was highly homologous at its amino terminus to SEF-17, the subunit protein of thin, aggregative fimbriae of Salmonella enteritidis 27655 strain 3b, suggesting that these fibres form a novel class of surface organelles on enterobacteria. E. coli HB101 is non-curliated and unable to bind soluble, iodinated fibronectin. The phenotypically cryptic curlin subunit gene, csgA, in HB101 is transcriptionally activated by expressing the cytoplasmic Crl on a multicopy plasmid. Transcriptional activation of csgA by Crl was observed after growth at 26 degrees C but not at 37 degrees C, even though crl transcription was not thermoregulated. A deletion of the 39 carboxy-terminal residues abolished Crl activity, whereas a deletion of 10 residues at the C-terminus did not, implying that a region between residue 93 and 122 in the 132-amino-acid-residue large Crl protein is required for activating curli expression in E. coli HB101. crl is a normal housekeeping gene in E. coli and it is suggested that its gene product may either be a DNA-binding protein affecting chromatin structure as has been suggested for histone-like protein H1 or interact with specific regulatory protein(s) controlling transcription of genes required for curli formation and fibronectin binding.
Department of Microbiology, University of Umeå, Sweden.
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Arnqvist
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Olsén
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Pfeifer
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DG
Russell
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Normark
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics* / Q000648:ultrastructure; D029968:Escherichia coli Proteins; D005353:Fibronectins / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D005798:Genes, Bacterial / Q000502:physiology*; D006358:Hot Temperature; D008969:Molecular Sequence Data; D015388:Organelles / Q000502:physiology; D014158:Transcription, Genetic / Q000502:physiology
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D005353:Fibronectins; C489688:csgA protein, E coli; C077481:Crl protein, Bacteria