Biochemistry Seminar: Seth Darst
Wed, Dec 04
12:00 PM — 1:00 PM
MarshakConvent Ave & 138th St
Seth Darst, Molecular Biophys, Rockefeller Univ, "Structural studies of bacterial transcription”Seth Darst, Professor, Dept of Molecular Biophysics, Rockefeller University, will give a talk titled, "Structural studies of bacterial transcription: Bacteriophage T7 Gp2 inhibition of E. coli RNA polymerase."
ABSTRACT: The study of Escherichia coli and its phages have provided much of the mechanistic foundations of our knowledge of transcription and its regulation. The last 14 years has seen enormous advances in our understanding of bacterial RNA polymerases (RNAPs) from landmark X-ray crystal structures of Thermus aquaticus and Thermus thermophilus RNAPs, but a detailed understanding of E. coli RNAP regulation has been lacking due to the inability to produce suitable crystals. Finally, this year several groups have provided us with structures of E. coli RNAP. Perhaps as expected, the apo structures of E. coli RNAP has not revealed any major surprises due to the high conservation of basic RNAP structure and function between all organisms. However, these results have opened the way to more detailed structure/function analyses of E. coli RNAP-specific regulators that can provide rich mechanistic information.
Bacteriophage T7 encodes an essential inhibitor of the E. coli host RNAP, the product of gene 2 (Gp2). We determined a series of X-ray crystal structures of E. coliRNAP-holoenzyme with or without Gp2. The results define the structure and location of the RNAP σ70 subunit domain 1.1 (σ70 1.1) inside the RNAP active site channel, where it must be displaced by the DNA upon formation of the open promoter complex. The structures and associated data, combined with previous results, allow a complete delineation of the mechanism for Gp2 inhibition of E. coli RNAP. In the primary inhibition mechanism, Gp2 forms a protein/protein interaction with σ70 1.1, preventing the normal egress of σ70 1.1 from the RNAP active site channel. Gp2 thus misappropriates a domain of the RNAP-holoenzyme, σ70 1.1, to inhibit the function of the enzyme.