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From Proteopedia
Crystal structure of the RfaH transcription factor at 2.1A resolution
Structural highlights
Function[RFAH_ECOLI] Enhances distal genes transcription elongation in a specialized subset of operons that encode extracytoplasmic components. RfaH is recruited into a multi-component RNA polymerase complex by the ops element, which is a short conserved DNA sequence located downstream of the main promoter of these operons. Once bound, RfaH suppresses pausing and inhibits Rho-dependent and intrinsic termination at a subset of sites. Termination signals are bypassed, which allows complete synthesis of long RNA chains. Enhances expression of several operons involved in synthesis of lipopolysaccharides, exopolysaccharides, hemolysin, and sex factor. Also negatively controls expression and surface presentation of AG43 and possibly another AG43-independent factor that mediates cell-cell interactions and biofilm formation.[1] [2] [3] [4] [5] [6] [7] [8] [9] 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 PubMedRfaH, a paralog of the general transcription factor NusG, is recruited to elongating RNA polymerase at specific regulatory sites. The X-ray structure of Escherichia coli RfaH reported here reveals two domains. The N-terminal domain displays high similarity to that of NusG. In contrast, the alpha-helical coiled-coil C domain, while retaining sequence similarity, is strikingly different from the beta barrel of NusG. To our knowledge, such an all-beta to all-alpha transition of the entire domain is the most extreme example of protein fold evolution known to date. Both N domains possess a vast hydrophobic cavity that is buried by the C domain in RfaH but is exposed in NusG. We propose that this cavity constitutes the RNA polymerase-binding site, which becomes unmasked in RfaH only upon sequence-specific binding to the nontemplate DNA strand that triggers domain dissociation. Finally, we argue that RfaH binds to the beta' subunit coiled coil, the major target site for the initiation sigma factors. Structural basis for converting a general transcription factor into an operon-specific virulence regulator.,Belogurov GA, Vassylyeva MN, Svetlov V, Klyuyev S, Grishin NV, Vassylyev DG, Artsimovitch I Mol Cell. 2007 Apr 13;26(1):117-29. PMID:17434131[10] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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