BIOCHEM 2B03 Lecture Notes - Lecture 13: Rna Polymerase Ii, Corepressor, Dna Gyrase
Document Summary
Regulatory proteins assemble subunits and activate rnap: promoter recognition. Rnap binds non-specifically to dna (low affinity; kd = 10-8 10-9 m) (of rnap holoenzyme) recognizes promoter sequence forms closed promoter sequence (kd = 10-14 m) Promoters are highly conserved; consensus sequences: pribnow box at -10. Rnap unwinds dna forms open promoter complex (kd = 10-13 m) At initiation site rnap initiates rna synthesis; binds first ntp within open promoter sequence (prefers atp and gtp; purines) Nuc attack of 3"-oh of 1st ntp on -p of incoming ntp pyrophosphate released and hydrolyzed by inorganic pyrophosphatase pppn1 + pppn2 pppn1pn2 + ppi (pppn = atp, ctp, gtp, utp as determined by dna template) Rna grows 6-10 units; falls off: chain elongation. Rnap core continues synthesis (elongation rate 20-50 bases/second; fairly accurate error rate 1/10 000 bases) pppn1pn2 + pppn3 pppn1pn2pn3 + ppi (pppn = atp, ctp, gtp, utp as determined by dna template) Supercoils form negative behind, positive ahead of transcription bubble.