9. 4 Sigma factor controls Holoenzyme Equilibrium binding to dna constant DNA binding 10M Closed binary com pl ex Rate constant DNA melting k2 Open Figure 9.9RNA 八入 bina com pl polymerase passes through Abortive Rate constant several steps prior to initiation c 10 sec elongation. A closed binary八八 complex is converted to an Release of Promoter open form and then into a sIgma clearance >1-2 sec ternary complex 入RNA synthes is egIns 消当
Figure 9.9 RNA polymerase passes through several steps prior to elongation. A closed binary complex is converted to an open form and then into a ternary complex. 9.4 Sigma factor controls binding to DNA
an d covers 75-envp Sins sigma In itiat on complex cont 9.4 Sigma factor 50-40-50-20-101+10+20+30 controls binding tO dNA 入0 I nitial ebngation complex farms at 10 bases. lases sgma, ad loses cantans in-3 to 55 regan 50-40-50-20-101+10+20+30 Figure 9 10 RNA polymerase initially contacts the region from -55 to +20. When sigma 入AO dissociates the core enzyme contracts to-30: when the General elongation complex enzyme moves a few base pairs foms at 15-20 bases and covers 30-40 bp it becomes more compactly 0-40-30-20-10 +10+20+30 organized into the general elongation complex 消当
Figure 9.10 RNA polymerase initially contacts the region from -55 to +20. When sigma dissociates,the core enzyme contracts to -30; when the enzyme moves a few base pairs, it becomes more compactly organized into the general elongation complex. 9.4 Sigma factor controls binding to DNA
9.4 Sigma factor 500-1000c0 enzymes a loose complexe controls binding tO dNA 5001000 L a loosey complexes t Figure 9. 11 Core free holoenzyme enzyme and ↓t 500-1000 holoenzyme are holoenzymes distributed on dna A^强 in closed open) complexes at promoters and very little rna 2500 core enzymes polymerase is free engaged in ranscription 消当
Figure 9.11 Core enzyme and holoenzyme are distributed on DNA, and very little RNA polymerase is free. 9.4 Sigma factor controls binding to DNA
Model Reaction 9.4 Sigma factor controls binding 入入A Random dittusion tO dNA to target 合导 sec N 入AA 14-1-1 Random c10 M sec diffusion to any DNA入A△A followed by 入AA Random Figure 9.12 How does displace ment between RNA polymerase find DNA 入AAA target promoters so rapidly on DNA? Sliding along Dna Does not occur 消当 八
Figure 9.12 How does RNA polymerase find target promoters so rapidly on DNA? 9.4 Sigma factor controls binding to DNA
Core enzvne 9.4 Sigma factor Fast. Slow stored on DNA controls binding 入O tO dNA Sigma Fast? fact associates with core enzyme Holoenzyme Fast has reduced affinity for loose sites Very fast Holoenzyme has ffinity fo promote rs Figure 9.13 Sigma very fast factor and core enzyme N Core zyme nth recycle at different RNA points in transcription. N Core enzyme a terminates 消当 and is re le ase d
Figure 9.13 Sigma factor and core enzyme recycle at different points in transcription. 9.4 Sigma factor controls binding to DNA