10.4 Mutations identify the operator and the regulator gene Figure 10.9 c/gene synthesizes defective repressor that Mutations that does not bind to DNA inactivate the lacl gene cause the operon to be constitutively expressed, NNNN入入NNNN八wNN八NNNN because the mutant repressor ↓ protein cannot bind to the Operon is transcribed and transated operator. h n 清菜大当
Figure 10.9 Mutations that inactivate the lacI gene cause the operon to be constitutively expressed, because the mutant repressor protein cannot bind to the operator. 10.4 Mutations identify the operator and the regulator gene
10.4 Mutations identify the operator and the regulator gene Inducer binding DNA binding Oligomerization ecis cannot oligomerge eci -d ec 50 100 150 200 250 300 350 Figure 10.10 Mutations map the regions of the lacl gene responsible for different functions.The DNA-binding domain is identified by lacl-d mutations at the N- terminal region;lacl mutations unable to form tetramers are located between residues 220-280.Other lacl mutations occur throughout the gene.lacls mutations occur in 清苇大当 regularly spaced clusters between residues 62-300
Figure 10.10 Mutations map the regions of the lacl gene responsible for different functions. The DNA-binding domain is identified by lacI-d mutations at the Nterminal region; lacl- mutations unable to form tetramers are located between residues 220-280. Other lacI- mutations occur throughout the gene. lacIs mutations occur in regularly spaced clusters between residues 62-300. 10.4 Mutations identify the operator and the regulator gene
10.5 Repressor protein binds to the operator and is released by inducer Figure 10.11 Constitutive mutations A TGTTA C ACAAT G A The lac operator 4 has a symmetrical sequence.The 4以4中 4 sequence is TGTTGT GTGGAATTGT GAG CGGATAACAATTT CACACA numbered relative ACAACACACCTTAACACTCGCCTATT GT TAAAGT GT GT to the startpoint for transcription .10 -5 +1 +10 +15 +20 +25 at+1.The regions +5 RN of dyad symmetry Axis of symmetry are indicated by IPurines protected by Purines where Thymines that can be repressor against methylation is ◆crosslinked to the shaded blocks methylation enhanced by repressor repressor 清菜大当
Figure 10.11 The lac operator has a symmetrical sequence. The sequence is numbered relative to the startpoint for transcription at +1. The regions of dyad symmetry are indicated by the shaded blocks. 10.5 Repressor protein binds to the operator and is released by inducer
10.5 Repressor protein binds to the operator and is released by inducer -35 se quence -10 se quence Start poirt Mo dification pr events RN A polyme rase 女卡k↓↓ kin ding 女wWW W↓+A区XXXX%↓ XX XX X灯GAC000000灯A TNontem plate stepd xxX 林0行 抄◆李tt李Unwindng RNA polymer ase XXXX鸡AC KXX0K006X0KXXA ◆orot ects agai ns过 Template straXX X Xx Imodification IA X XX X M ost points of contact lie on o ne face of DNA(on the nonte mplate strand Mutations abolish or reduce promoter activity Figure 9.16 One face of the promoter contains the contact points for RNA. 清菜大当
Figure 9.16 One face of the promoter contains the contact points for RNA. 10.5 Repressor protein binds to the operator and is released by inducer
Inducer binds to free Inducer binds 10.5 Repressor protein binds to repressor to upset directly to release equilibrium with bound repressor from the operator and is released by repressor operator inducer 闪八入N八N风八入N八N Figure 10.12 Does the inducer bind to free repressor to upset an equilibrium (left) or directly to repressor bound at the operator (right)? 清菜大当
Figure 10.12 Does the inducer bind to free repressor to upset an equilibrium (left) or directly to repressor bound at the operator (right)? 10.5 Repressor protein binds to the operator and is released by inducer