Journal Article


Stephen G J Smith
Cyril J Smyth
Vivienne Mahon



fimbriae bacterial genetics chemistry amino acid sequence mutagenesis molecular sequence data enterotoxigenic escherichia coli rns protein bacteria trans activators metabolism helix turn helix motifs sequence deletion genes regulator gene expression regulation bacterial

Mutagenesis of the Rns regulator of enterotoxigenic Escherichia coli reveals roles for a linker sequence and two helix-turn-helix motifs. (2010)

Abstract The pathogenesis of diarrhoeal disease due to human enterotoxigenic Escherichia coli absolutely requires the expression of fimbriae. The expression of CS1 fimbriae is positively regulated by the AraC-like protein Rns. AraC-like proteins are DNA-binding proteins that typically contain two helix-turn-helix (HTH) motifs. A program of pentapeptide insertion mutagenesis of the Rns protein was performed, and this revealed that both HTH motifs are required by Rns to positively regulate CS1 fimbrial gene expression. Intriguingly, a pentapeptide insertion after amino acid C102 reduced the ability of Rns to transactivate CS1 fimbrial expression. The structure of Rns in this vicinity (NACRS) was predicted to be disordered and thus might act as a flexible linker. This hypothesis was confirmed by deletion of this amino acid sequence from the Rns protein; a truncated protein that lacked this sequence was no longer functional. Strikingly, this sequence could be functionally substituted in vivo and in vitro by a flexible seven amino acid sequence from another E. coli AraC-like protein RhaS. Our data indicate that HTH motifs and a flexible sequence are required by Rns for maximal activation of fimbrial gene expression.
Collections Ireland -> Trinity College Dublin -> PubMed

Full list of authors on original publication

Stephen G J Smith, Cyril J Smyth, Vivienne Mahon

Experts in our system

Stephen Smith
Trinity College Dublin
Total Publications: 27