BIOB11H3 Lecture Notes - Lecture 9: Lac Repressor, Lac Operon, Camp Receptor Protein
Document Summary
Lactose = disaccharide of galactose + glucose covalently linked together. Lactose (act as an inducer) -galactosidase expressed lactose metabolized into glucose + galactose. Rapid expression of -galactosidase mrna after inducer is added. Mrna level crashes when inducer is eliminated level of -galactosidase will fall after time (not shown in graph) Colle(cid:272)tio(cid:374) of (cid:272)o(cid:373)po(cid:374)e(cid:374)ts that(cid:859)s (cid:396)espo(cid:374)si(cid:271)le to o(cid:396)ga(cid:374)ize (cid:396)espo(cid:374)se to a particular stimulus. Regulatory gene encode for regulatory protein which interact operator sequence. Control the expression of structural genes (code for enzymes of the same metabolic pathway) Repressor protein is active when its translated, will be inactivated when bound to lac. When lactose is present, it binds to repressor and inactivate it. Translation of mrna yields 3 enzymes that convert lactose to glucose & galactose. Binding of lactose to lac repressor is transient, Repressor now able to bind to operator. Cis (cid:448)s t(cid:396)a(cid:374)s: (cid:862)cis-acting promotor sequence to which a trans-a(cid:272)ti(cid:374)g t(cid:396)a(cid:374)s(cid:272)(cid:396)iptio(cid:374) fa(cid:272)to(cid:396) (cid:271)i(cid:374)ds(cid:863)
