BSC 315 Lecture Notes - Lecture 17: Dna Binding Site, Operon, Lac Repressor

• School: University of Alabama
• Department: Biological Sciences
• Course: BSC 315
• Professor: Edwin Stephenson

Document Summary

Lactose binding (bound lactose inactivates dna binding activity allosterically) All laci mutations to date are nulls- complete loss of repressor- protein/loss of dna binding activity (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) Behavior- binds to operator whether lactose is present or not. Phenotype- represses expression when lactose is absent & when it"s present. This laci mutation known as lacis (s = super repressor) The lac repressor has 2 functional binding sites: Dna binding site: binds to operator. The lac repressor switches back & forth between 2 forms: Lactose absent- repressor binds to the operator. Lactose present- operator binding site is inactivated. The lac repressor switches back & forth between 2 states depending on the availability of lactose. No lactose operon binding site is functional. Lactose operon binding site not functional (cid:1) Normal laci mutants produce repressor protein that is incapable of binding to operator (cid:1)