title: X-ray crystal structure of the polymerase domain of the bacteriophage N4 virion RNA polymerase.
abstract: Coliphage N4 virion RNA polymerase (vRNAP), which is injected into the host upon infection, transcribes the phage early genes from promoters that have a 5-bp stem-3 nt loop hairpin structure. Here, we describe the 2.0-A resolution x-ray crystal structure of N4 mini-vRNAP, a member of the T7-like, single-unit RNAP family and the minimal component having all RNAP functions of the full-length vRNAP. The structure resembles a "fisted right hand" with Fingers, Palm and Thumb subdomains connected to an N-terminal domain. We established that the specificity loop extending from the Fingers along with W129 of the N-terminal domain play critical roles in hairpin-promoter recognition. A comparison with the structure of the T7 RNAP initiation complex reveals that the pathway of the DNA to the active site is blocked in the apo-form vRNAP, indicating that vRNAP must undergo a large-scale conformational change upon promoter DNA binding and explaining the highly restricted promoter specificity of vRNAP that is essential for phage early transcription.
authors: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA. kum14@psu.edu
authors: Katsuhiko S
authors: KS
authors: Murakami
authors: Elena K
authors: EK
authors: Davydova
authors: Lucia B
authors: LB
authors: Rothman-Denes
mesh_terms: D025522:Bacteriophage N4 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004247:DNA / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D014771:Virion / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D004247:DNA; D012321:DNA-Directed RNA Polymerases