ISSN:
1365-2958
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
,
Medicine
Notes:
A model for the domain structure of σ54-dependent transcriptional activators, based on sequence data, has been tested by examining the function of truncated and chimaeric proteins. Removal of the N-terminal domain of NtrC abolishes transcriptional activation, indicating that this domain is positively required for activator function. Over-expression of this domain as a separate peptide appears to titrate out the phosphorylating activity of NtrB. Removal of the N-terminal domain of NifA reduces activation 3–4-fold. The residual activity is particularly sensitive to inhibition by NifL, suggesting that the role of the N-terminal domain is to block the action of NifL in derepressing conditions. The C-terminal domain of NtrC showed repressor activity when expressed as a separate peptide. This domain is necessary for activator function even when NtrC binding sites are deleted from promoters. A point mutation in the ATP-binding motif of the NtrC central domain, Ser 169 to Ala, also abolished activator function. Exchanging the N-terminal domains of Klebsiella pneumoniae NtrC, NifA and Escherichia co/r OmpR, did not produce any hybrid activity, suggesting that N-terminal domains in the native proteins specifically recognize the rest of the molecule.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2958.1990.tb02012.x
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