Monday, 23 May 2005 - 2:15 PM

This presentation is part of: Gene Expression: Transcription

Structure of bacterial RNA polymerase holoenzyme complexed with streptolydigin

Eddy Arnold1, Steven Tuske2, Stefan G. Sarafianos1, Xinyue Wang2, Brian Hudson2, E. Sineva2, Jayanta Mukhopadhay1, Jens J. Birktoft2, Oliver Leroy2, Sajida Ismail2, Arthur D. Clark Jr.1, Chhaya Dharia1, Andrew Napoli1, Oleg Laptenko3, Jookyung Lee3, Sergei Borukhov3, and Richard H. Ebright2. (1) Rutgers University, Piscataway, NJ, (2) Rutgers University, Piscataway, NJ, (3) UMDNJ, Stratford, NJ

RNA polymerase (RNAP) is the key enzyme of transcription. Bacterial RNAP core (subunits: ααββ'ω) binds a σ factor to form the RNAP holoenzyme (RNAPh)(ααββ'ωσ, MW~450 KDa), which is capable of specific promoter recognition and initiation of transcription. Streptolydigin (Stl) is an antibiotic that inhibits RNAP. Using saturation mutagenesis of the β and β' RNAP genes we have isolated and characterized Stl-resistant mutants with changes at a region proximal to the ”bridge helix” and “trigger loop”. We have solved the 3.0 Å resolution crystal structure of T. thermophilus RNAPh complexed with Stl. Stl makes several contacts with resistance mutation sites on the bridge-helix and trigger-loop. The observed bridge-helix conformation is similar to that seen in eukaryotic RNAP II but different from that in structures of bacterial RNAP. It has been proposed that RNAP cycles between straight and bent bridge-helix conformations during RNAP translocation. We propose that Stl inhibits RNAP by blocking cycling between straight and bent bridge-helix conformations thereby blocking translocation. Authors represent the the following units. 1. Department of Chemistry and Chemical Biology, Rutgers University, Piscataway NJ 08854, USA 2. Center for Advanced Biotechnology and Medicine, Rutgers University, Piscataway NJ 08854, USA 3. Waksman Institute, Rutgers University, Piscataway NJ 08854, USA 4. Howard Hughes Medical Institute, Piscataway NJ 08854, USA 5. Department of Cell Biology, UMDNJ, Stratford NJ 08084, USA

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