MBIO 2020 Lecture Notes - Lecture 10: Camp Receptor Protein, In Silico, Repressor
10 Nov 2016
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Document Summary
Trp operon is repressible, lac operon is inducible. Presence of trp activates regulator and no enzymes. Presence of lactose induces the expression of lac operon. The actual inducer is not lactose itself. Lac i (reg) - structural gene encoding constitutive repressor - function. P - promoter - binds rna pol. O - operator - binds active lac l repressor. Lac z - lac a - structural genes - encode enzymes required for lac biosynthesis: transcribed as a polycistronic mrna, lac z - beta-galatosidase, lac y - lac permease, lac a - transacetylase. Enzymes for lactose catabolism are not required. Lac repressor - functional - specifically binds to o. Prevents rna pol from binding to p. Lac z laca - transcription of these are blocked: lac operon is repressed. 2 dimers of lac i protein bind together - tetramer - to 2 operators sequences that precede the cluster of lac structural genes.
