8pfg | pdb_00008pfg
autoinhibited RfaH bound to E. coli transcription complex paused at ops site (encounter complex), not fully complementary scaffold
Structural highlights
FunctionRFAH_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] Publication Abstract from PubMedRfaH, a paralog of the universally conserved NusG, binds to RNA polymerases (RNAP) and ribosomes to activate expression of virulence genes. In free, autoinhibited RfaH, an alpha-helical KOW domain sequesters the RNAP-binding site. Upon recruitment to RNAP paused at an ops site, KOW is released and refolds into a beta-barrel, which binds the ribosome. Here, we report structures of ops-paused transcription elongation complexes alone and bound to the autoinhibited and activated RfaH, which reveal swiveled, pre-translocated pause states stabilized by an ops hairpin in the non-template DNA. Autoinhibited RfaH binds and twists the ops hairpin, expanding the RNA:DNA hybrid to 11 base pairs and triggering the KOW release. Once activated, RfaH hyper-stabilizes the pause, which thus requires anti-backtracking factors for escape. Our results suggest that the entire RfaH cycle is solely determined by the ops and RfaH sequences and provide insights into mechanisms of recruitment and metamorphosis of NusG homologs across all life. Concerted transformation of a hyper-paused transcription complex and its reinforcing protein.,Zuber PK, Said N, Hilal T, Wang B, Loll B, Gonzalez-Higueras J, Ramirez-Sarmiento CA, Belogurov GA, Artsimovitch I, Wahl MC, Knauer SH Nat Commun. 2024 Apr 8;15(1):3040. doi: 10.1038/s41467-024-47368-4. PMID:38589445[10] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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