ISSN:
1365-2958
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
,
Medicine
Notes:
The promoters of the Escherichia coli Maltose regulon are positively regulated by the MaIT protein, which recognizes a short asymmetric nucleotide sequence that is present as several copies in each promoter of the regulon. We report a detailed biochemical characterization of the interaction of MaIT with the promoter of the malPQ operon. The MaIT sites in malPp were precisely located and their occupation as a function of MaiT concentration was quantified using DNase I and dimethyl sulphate footprinting experiments. The contribution of each site to malPp activity was assessed by Introducing mutations that destroy them and measuring the residual in vivo and in vitro activity. Two main results were obtained. First, although the proximal MaIT site is centred at -37.5, RNA polymerase is likely to establish a contact required for matPp activity with at least one base pair of the promoter -35 region; this close proximity between RNA polymerase and MaIT bound to site 1 suggests that the two proteins interact. Second, even if the interaction of MaIT with the three functional sites in maIPp is a co-operative process, the MaIT molecules bound to the two distal sites play a more subtle rote than simply increasing the occupancy of the proximal site and may also contact RNA polymerase. We suggest that, in the nucleoprotein structure responsible for the initiation of transcription, MaIT, RNA polymerase and malPp are held together by several weak interactions.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2958.1994.tb01294.x
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