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Cassette mutagenesis implicates a helix‐turn‐helix motif in promoter recognition by the novel RNA polymerase Sigma factor σ 54
Author(s) -
Coppard J. R.,
Merrick M. J.
Publication year - 1991
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1991.tb00777.x
Subject(s) - biology , mutant , footprinting , sigma factor , rna polymerase , specificity factor , promoter , site directed mutagenesis , microbiology and biotechnology , helix turn helix , mutagenesis , polymerase , genetics , rna , gene , transcription factor , gene expression , dna binding protein
Summary Cassette mutagenesis has been used to study the role of a helix‐turn‐helix (HTH) motif in the novel RNA polymerase sigma factor σ 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 σ 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 foot‐printing indicated that the inactive HTH mutants of a54 were defective in interaction with both the ‐24 and ‐12 regions of the gln Ap2 promoter.