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Crystal structure of sigm54 activator (AAA+ ATPase) in the inactive stateCrystal structure of sigm54 activator (AAA+ ATPase) in the inactive state
Structural highlights
Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedTranscription by sigma54 RNA polymerase depends on activators that contain ATPase domains of the AAA+ class. These activators, which are often response regulators of two-component signal transduction systems, remodel the polymerase so that it can form open complexes at promoters. Here, we report the first crystal structures of the ATPase domain of an activator, the NtrC1 protein from the extreme thermophile Aquifex aeolicus. This domain alone, which is active, crystallized as a ring-shaped heptamer. The protein carrying both the ATPase and adjacent receiver domains, which is inactive, crystallized as a dimer. In the inactive dimer, one residue needed for catalysis is far from the active site, and extensive contacts among the domains prevent oligomerization of the ATPase domain. Oligomerization, which completes the active site, depends on surfaces that are buried in the dimer, and hence, on a rearrangement of the receiver domains upon phosphorylation. A motif in the ATPase domain known to be critical for coupling energy to remodeling of polymerase forms a novel loop that projects from the middle of an alpha helix. The extended, structured loops from the subunits of the heptamer localize to a pore in the center of the ring and form a surface that could contact sigma54. Regulation of the transcriptional activator NtrC1: structural studies of the regulatory and AAA+ ATPase domains.,Lee SY, De La Torre A, Yan D, Kustu S, Nixon BT, Wemmer DE Genes Dev. 2003 Oct 15;17(20):2552-63. PMID:14561776[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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