LIFESCI 3 Chapter Notes - Chapter 20.1: Camp Receptor Protein, Arabinose, Base Pair
Document Summary
Control of transcription allows control of protein levels and synchronized regulation of multiple genes encoding products with interdependent activities. Variations in promoter sequences and the space between promoters and genes affect translation efficiency. The lac operon is subject to negative regulation. E coli use different enzymes to metabolize different sugars. Genes are grouped together into an operon genes are coordinately regulated. Lac operon: includes lacz ( -galactosidase), lacy (galactoside permease) and laca (thiogalactoside transacetylase) Transcribed in one unit but has 3 ribosome binding sites independent translation of each protein. Transcription is reduced when lactose is unavailable. Galactosidase: catalyzes cleavage of lactose into glucose and galactose which are metabolized to generate atp. Galactoside permease: inserts into plasma membrane and imports lactose into cell. Thiogalactoside transacetylase: modifies toxic galactosides for removal from the cell. Mutations of laci or laco lead to constitutive expression of the operon whether lactose was present or not. Jacob and monod combined wild type strains with mutants.
