Properties of a mutant form of the prokaryotic enhancer binding protein, NTRC, which hydrolyses ATP in the absence of effectors

The mutation S170A in the proposed nucleotide binding site of the transcriptional activator protein NTRC abolishes its ability to catalyse open promoter complex formation by the sigma(N)-RNA polymerase holoenzyme, NTRCS170A has significant ATPase activity, which, in contrast to the wad-type protein, is unaffected by phosphorylation or binding to enhancer sites on DNA, The mutant protein appears to oligomerise normally on DNA in response to phosphorylation hut the ATPase activity is apparently nat responsive to changes in oligomerisation state, The defect in transcriptional activation is discussed in relation to mutations in other sigma(N)-dependent activators. (C) 1998 Federation of European Biochemical Societies.