ISSN:
1365-2958
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Biologie
,
Medizin
Notizen:
Rhizobium melioti DctD activates transcription from the dctA promoter by catalysing the isomerization of closed complexes between σ54-RNA polymerase holoenzyme and the promoter to open complexes. DctD must make productive contact with σ54-holoenzyme and hydrolyse ATP to catalyse this isomerization. To define further the activation process, we sought to isolate mutants of DctD that had reduced affinities for σ54-holoenzyme. Mutagenesis was confined to the well-conserved C3 region of the protein, which is required for coupling ATP hydrolysis to open complex formation in σ54-dependent activators. Mutant forms of DctD that failed to activate transcription and had substitutions in the C-terminal half of the C3 region were efficiently cross-linked to σ54 and the β-subunit of RNA polymerase, suggesting that they bound normally to σ54-holoenzyme. In contrast, some mutant forms of DctD with amino acid substitutions in the N-terminal half of the C3 region had reduced affinities for σ54 and the β-subunit in the cross-linking assay. These data suggest that the N-terminal half of the C3 region of DctD contains a site that may contact σ54-holoenzyme during open complex formation.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1046/j.1365-2958.1997.5851955.x
Permalink
