Arnqvist A, Olsén A, Pfeifer J, Russell D G, Normark S
Department of Microbiology, University of Umeå, Sweden.
Mol Microbiol. 1992 Sep;6(17):2443-52. doi: 10.1111/j.1365-2958.1992.tb01420.x.
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.
卷曲菌毛是结合纤连蛋白的大肠杆菌上的细的、螺旋状的、温度调节性纤维。卷曲菌毛的亚基蛋白在其氨基末端与肠炎沙门氏菌27655菌株3b的细的聚集菌毛的亚基蛋白SEF-17高度同源，这表明这些纤维在肠道细菌上形成了一类新的表面细胞器。大肠杆菌HB101不产生卷曲菌毛，并且不能结合可溶性的、碘化的纤连蛋白。通过在多拷贝质粒上表达细胞质中的Crl，可以转录激活HB101中表型隐匿的卷曲菌毛亚基基因csgA。在26℃生长后观察到Crl对csgA的转录激活，但在37℃时未观察到，尽管crl转录不受温度调节。缺失39个羧基末端残基消除了Crl活性，而在C末端缺失10个残基则没有，这意味着在132个氨基酸残基的大Crl蛋白中，93至122位残基之间的区域是激活大肠杆菌HB101中卷曲菌毛表达所必需的。crl是大肠杆菌中的一个正常管家基因，有人认为其基因产物可能要么是一种影响染色质结构的DNA结合蛋白，就像组蛋白样蛋白H1那样，要么与控制卷曲菌毛形成和纤连蛋白结合所需基因转录的特定调节蛋白相互作用。
