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Functional roles of the pre-sensor I insertion sequence in an AAA+ bacterial enhancer binding protein.

Mol Microbiol. 2009 Aug;73(4):519-33. Epub 2009 May 25
Patricia C Burrows 1 , Jörg Schumacher , Samuel Amartey , Tamaswati Ghosh , Timothy A Burgis , Xiaodong Zhang , B Tracy Nixon , Martin Buck
Patricia C Burrows 1 , Jörg Schumacher , Samuel Amartey , Tamaswati Ghosh , Timothy A Burgis , Xiaodong Zhang , B Tracy Nixon , Martin Buck
+ et al

[No authors listed]

Author information
  • 1 Department of Life Sciences, Division of Biology, Imperial College London, London, UK.

摘要


Molecular machines belonging to the AAA+ superfamily of ATPases use NTP hydrolysis to remodel their versatile substrates. The presence of an insertion sequence defines the major phylogenetic pre-sensor I insertion (pre-SIi) AAA+ superclade. In the bacterial sigma(54)-dependent enhancer binding protein phage shock protein F (PspF) the pre-SIi loop adopts different conformations depending on the nucleotide-bound state. Single amino acid substitutions within the dynamic pre-SIi loop of PspF drastically change the ATP hydrolysis parameters, indicating a structural link to the distant hydrolysis site. We used a site-specific protein-DNA proximity assay to measure the contribution of the pre-SIi loop in sigma(54)-dependent transcription and demonstrate that the pre-SIi loop is a major structural feature mediating nucleotide state-dependent differential engagement with Esigma(54). We suggest that much, if not all, of the action of the pre-SIi loop is mediated through the L1 loop and relies on a conserved molecular switch, identified in a crystal structure of one pre-SIi variant and in accordance with the high covariance between some pre-SIi residues and distinct residues outside the pre-SIi sequence.