10.4 Mutations identify the operator and the regulator gene Figure 10.9 fac gene synthesizes Mutations that defective re pressor that does not bind to dna inactivate the lacl gene cause the operon to be constitutively expressed 入 MV because the mutant repressor protein cannot bind to the Operon is transcribed and translated operator 消当
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 闷C canr oligomerize 闷C 闷C 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 lacl mutations occur in 请莘大 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 GTTA C T ACAAT G The lac operator ↓ has a symmetrical sequence. The sequence Is TGTTGTGTGGAATTGT GAGCGGATAACAATT T CACACA numbered relative ACAACACACCTTAACACTCGCCT ATT GTT AAAGTGTGT to the startpoint for transcription 10 +10 15 at +l. The regions of dyad symmetry Axis of symme are indicated by Purines protected的 Purines where Thymines that can be repressor against crosslinked to the shaded blocks. methylation methylat ion is enhanced by repressor repressor 请莘大
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 quenc -10 se quence Start poirt Mo di fication rr events RN A polyme rase ↓↓↓↓↓ ng bin din ↓ww↓ ↓W↓队XXXx%↓ xxXX XKTG ACXXOooxxxXXXXT ATNontem plate sti 444乎 伞今伞乎 Unwinding RNA polymer ase ( xxXX× &C T GxKxxx×0×X4TA prot ects aga nst emplate丈tc% XXXXX mod ification 属 xxxX M ost points of contact lie an one face of DNA(on the onte mplate str and Mutations abolish or reduce promoter activit Figure 9 16 One face of the promoter contains the contact points for RNa 请莘大
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 八 MM Figure 10.12 Does the inducer bind to free ■■■■ repressor to upset an equilibrium (left) or directly to ■■■■ repressor bound at the operator (right) 请莘大
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