Send to

Choose Destination
Mol Microbiol. 1991 Jun;5(6):1309-17.

Cassette mutagenesis implicates a helix-turn-helix motif in promoter recognition by the novel RNA polymerase sigma factor sigma 54.

Author information

AFRC Nitrogen Fixation Laboratory, University of Sussex, Brighton, UK.


Cassette mutagenesis has been used to study the role of a helix-turn-helix (HTH) motif in the novel RNA polymerase sigma factor sigma 54 of Klebsiella pneumoniae. Of the four residues which are predicted to be solvent-exposed in the second helix, the first (Glu-378) tolerated all substitutions, and some mutations of this residue increased expression from sigma 54-dependent promoters. Certain substitutions in the third exposed residue (Ser-382) produced a promoter-specific phenotype and all substitutions in the fourth residue (Arg-383) inactivated the protein, identifying this residue as being likely to be involved in base-specific interactions with the promoter. In vivo footprinting indicated that the inactive HTH mutants of sigma 54 were defective in interaction with both the -24 and -12 regions of the glnAp2 promoter.

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Wiley
Loading ...
Support Center