10.3 Repressor is controlled by a small molecule inducer Allosteric control refers to the ability of an interaction at one site of a protein to influence the activity of another site Coordinate regulation refers to the common control of a group of genes Corepressor is a small molecule that triggers repression of transcription by binding to a regulator protein Gratuitous inducers resemble authentic inducers of transcription but are not substrates for the induced enzymes Inducer is a small molecule that triggers gene transcription by binding to a regulator protein Induction refers to the ability of bacteria (or yeast)to synthesize certain enzymes only when their substrates are present; applied to gene expression, refers to switching on transcription as a result of interaction of the inducer with the regulator protein Repression is the ability of bacteria to prevent synthesis of certain enzymes when their products are present; more generally, refers to inhibition of transcription (or translation) by binding of repressor protein to a specific site on dNA (or mRNA) 请莘大
Allosteric control refers to the ability of an interaction at one site of a protein to influence the activity of another site. Coordinate regulation refers to the common control of a group of genes. Corepressoris a small molecule that triggers repression of transcription by binding to a regulator protein. Gratuitous inducersresemble authentic inducers of transcription but are not substrates for the induced enzymes. Inducer is a small molecule that triggers gene transcription by binding to a regulator protein. Induction refers to the ability of bacteria (or yeast) to synthesize certain enzymes only when their substrates are present; applied to gene expression, refers to switching on transcription as a result of interaction of the inducer with the regulator protein. Repression is the ability of bacteria to prevent synthesis of certain enzymes when their products are present; more generally, refers to inhibition of transcription (or translation) by binding of repressor protein to a specific site on DNA (or mRNA). 10.3 Repressor is controlled by a small molecule inducer
10.3 Repressor is controlled by a small molecule inducer Add inducer Remove inducer Level of fac mRNA Induced level Figure 10.6 Addition of Basal level Basal level inducer results in rapid 6 nin induction of lac mRNA, and is followed after a Level of B-galactosidase short lag by synthesis of ag the enzymes; removal of Induced level inducer is followed by rapid cessation of synthesis 请莘大 Basal level
Figure 10.6 Addition of inducer results in rapid induction of lac mRNA, and is followed after a short lag by synthesis of the enzymes; removal of inducer is followed by rapid cessation of synthesis. 10.3 Repressor is controlled by a small molecule inducer
10.3 Repressor is controlled by a small molecule inducer NO INDUCER: STRUCTURAL GENES REPRESSED Repressor tetra Figure 10.7 Repressor maintains the lac operon in the inactive 入 A condition by binding to lacz lacy facA INDUCER SWITCHES GENES the operator: addition of inducer releases the eactive form that cannot bind repressor. and thereby operator Inactive repressor allows rna 八wwA polymerase to initiate transcription 请莘大 ..e.a
Figure 10.7 Repressor maintains the lac operon in the inactive condition by binding to the operator; addition of inducer releases the repressor, and thereby allows RNA polymerase to initiate transcription. 10.3 Repressor is controlled by a small molecule inducer
10.4 Mutations identify the operator and the regulator gene Interallelic complementation describes the change in the properties of a heteromultimeric protein brought about by the interaction of subunits coded by two different mutant alleles; the mixed protein may be more or less active than the protein consisting of subunits only of one or the other type Negative complementation occurs when interallelic complementation allows a mutant subunit to suppress the activity of a wild-type subunit in a multimeric protein 请莘大
Interallelic complementation describes the change in the properties of a heteromultimeric protein brought about by the interaction of subunits coded by two different mutant alleles; the mixed protein may be more or less active than the protein consisting of subunits only of one or the other type. Negative complementation occurs when interallelic complementation allows a mutant subunit to suppress the activity of a wild-type subunit in a multimeric protein. 10.4 Mutations identify the operator and the regulator gene
10.4 Mutations identify the operator and the regulator gene Figure 10.8 Operator mutations are constitutive because the operator is unable to bind 血收自事卡只 ctive repressor cannot bind to o mutant operator repressor protein; this allows rna polymerase to have 入 M unrestrained access to the promoter. The Oc o operator mutations are ciS- O peron is transcribed acting, because they and translated affect only the contiguous set of ↓ structural genes 请莘大
Figure 10.8 Operator mutations are constitutive because the operator is unable to bind repressor protein; this allows RNA polymerase to have unrestrained access to the promoter. The Oc mutations are cisacting, because they affect only the contiguous set of structural genes. 10.4 Mutations identify the operator and the regulator gene