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). 清菜大兰
Allosteric controlrefers 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 0 4 6 8 1012 min induction of lac mRNA, and is followed after a Level of B-galactosidase short lag by synthesis of Lag Lag the enzymes;removal of Induced level inducer is followed by rapid cessation of synthesis. 清菜大当 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 tetramer repre ssor honm Figure 10.7 Repressor maintains the lac Tetramer binds to operator DNA operon in the inactive condition by binding to Prom oter Operator facz lacy facA INDUCER SWITCHES GENES ON the operator;addition of inducer releases the repressor,and thereby active repre ssor allows RNA RNA polymerase to initiate bindsat mRNA transcription mRNA is wotoogooo gogfooeooin 清菜大当 B-galactosidase Pemease Transacetylase proteins
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. 情華大当
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 Active repressor is unable to bind cannot bind to O mutant operator repressor protein;this allows RNA polymerase to have LUU002020八NUL0不N unrestrained access to the promoter.The Oc O operator ↓ mutations are cis- O peron is transcribed acting,because they and transated affect only the contiguous set of structural genes. w w w 清第大当
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