THE STRUCTURAL BASIS FOR nif GENE ACTIVATION

摘要

The nif genes from Klebsiella pneumoniae were amongst the first bacterial genes described whose activation required an ATP hydrolysing AAA (ATPases Associated with various cellular Activities) transcriptional activator proteins (also called Enhancer Binding Protein or EBPs, for example the NifA protein). The EBPs act in concert with the RNA polymerase (RNAP) containing the sigma (sigma) 54 promoter specificity factor. Here, we present some recent advances in understanding how ATP hydrolysis is used to change the functional state of the sigma~(54)-RNAP closed promoter complex in order to allow DNA opening (open promoter complex formation) and transcription initiation (Fig. 1). These results help us understand how the ATP induced conformational changes in the AAA activator are used to induce alterations in the sigma~(54)-RNAP closed complex. Evidently, ATP hydrolysis is used by the AAA activator to induce a series of directed conformational changes (i.e. remodelling) in sigma~(54)-RNAP closed complex, rather than to allow a simple ATP conditioned binding of the interacting partners.