The lactose lac operon — an example for

The lactose (lac) operon - an example for prokaryotic gene regulation

1. Nobel prize for the discovery of lac operon - 1965 Francois Jacob Jacques Monod Pasteur Institute, Paris, France

The structure of lac operon 2. E. coli DNA operon promoter DNA P lac. I E C promoter O repressor CAP site RNA pol operator binding site Structural geneslac. A lac. Z lac. Y structural genes T DNA terminator catabolit activator protein binding site Cytoplasm cell wall outer world

Structure lac operon 3.

Repression C DNA P lac. I repressor E O lac. Z CAP site entry site operator rep: repressor pol: RNA polymerase pol lac. Y structural genes 4. lac. A T terminator DNA

Induction C DNA P lac. I repressor E O rep lac. Z CAP site entry site operator glucose galactose rep: repressor pol: RNA polymerase 5. lac. Y structural genes lac. A T terminator DNA

Induction C DNA P lac. I repressor E O rep lac. Z CAP site entry site operator pol rep: repressor pol: RNA polymerase 5. lac. Y structural genes b-gal T lac. A DNA terminator permease transacetylase

Activation DNA P lac. I CA P repressor c. AMP C E O lac. Z CAP site entry site operator lac. Y 6. lac. A structural genes CAP: catabolite activator protein No glucose T terminator DNA

Activation DNA P lac. I E O lac. Z CAP site entry site operator CA P repressor C pol c. AMP No glucose lac. Y structural genes 6. lac. A T terminator DNA

Activation CA P 6. DNA P lac. I repressor C pol E O lac. Z CAP site entry site operator b-gal lac. Y lac. A structural genes permease T DNA terminator transacetylase

Activation DNA P lac. I E lac. Z O CAP site entry site operator lac. Y structural genes CA P repressor C pol catabolite repression (endproduct inhibition) No c. AMP Glucose is present 6. lac. A T terminator DNA

Structure and operation of lac operon Combined regulation P CA DNA P lac. I repressor C 7. pol E lac. Z O CAP site entry site operator lac. Y lac. A structural genes T DNA terminator Glucose - rep permease b-gal trans- Lactose + acetylase lactose adenylate cyclase glucose lactose adenylate cyclase c. AMP ATP cyclic AMP allolactose (inductor!)

8. Mutant beta-gal DNA P lac. I repressor C E O lac. Z CAP site entry site operator lac. Y structural genes lac. A T DNA terminator Glucose CA P Lactose + pol c. AMP No glucose rep

8. CA P Mutáns béta-gal DNA P lac. I repressor C pol E O lac. Z CAP site entry site operator lac. Y lac. A structural genes T DNA terminator Glucose b-gal* lactose permease Lactose + transacetylase

9. CA P Transcription stop in genes DNA P lac. I repressor C pol E O lac. Z CAP site entry site operator stop lac. A lac. Y structural genes T terminator transcription stop rep b-gal permease DNA Glucose Lactose +

9. CA P Transcription stop in genes DNA P lac. I repressor C pol E O lac. Z CAP site entry site operator stop lac. Y structural genes lac. A T DNA terminator Glucose - rep Lactose + b-gal

9. CA P Transcription stop in genes DNA P lac. I repressor rep C pol E O stop lac. Z CAP site entry site operator lac. Y structural genes lac. A T DNA terminator Glucose Lactose +

The Oc 10. mutation of operon The operator is not able to bind the repressor pol DNA P lac. I repressor C E Oc lac. Z CAP site entry site operator lac. Y T lac. A structural genes DNA terminator CA P Glucose - rep pol b-gal permease trans. Lactose acetylase

The I- mutation of repressor 11. The repressor is not able to bind to the operator pol DNA P lac. I repressor E C O lac. Z CAP site entry site operator lac. Y T lac. A structural genes DNA terminator CA P Glucose - rep pol b-gal permease trans. Lactose acetylase

The Is mutation of repressor 12. The repressor is unable to bind lactose pol DNA P lac. I* repressor E C O lac. Z CAP site entry site operator lac. Y structural genes lac. A T DNA terminator Glucose CA P Lactose + rep pol

13. Mutant CAP-I CAP is unable to bind c. AMP DNA P lac. I repressor C E O lac. Z CAP site entry site operator lac. Y structural genes lac. A T DNA terminator Glucose CA P Lactose + c. AMP No glucose

13. Mutant CAP-I CAP is unable to bind c. AMP DNA P lac. I repressor C E O lac. Z CAP site entry site operator lac. Y structural genes lac. A T DNA terminator Glükóz CA P Laktóz + pol c. AMP No glucose

14. Mutant CAP-II CAP can bind promoter in the absence of c. AMP pol C DNA P lac. I repressor E O lac. Z CAP site entry site operator lac. Y T lac. A structural genes DNA terminator CA P Glucose + pol rep b-gal permease trans. Lactose + acetylase

15. Too many repressors C DNA P lac. I repressor rep Orep lac. Z E CAP site entry site operator lac. Y lac. A structural genes DNA T terminator rep Glucose CA P DNA P lac. I plasmid rep pol Lactose + DNA P lac. I plasmid rep DNA P lac. I rep Repressor plasmid rep DNA P lac. I plasmid – on the plasmid

16. Too many operators pol represssor E C DNA P lac. I lac. Z O CAP site entry site operator lac. Y lac. A structural genes DNA T terminator Glucose CA P rep DNA O O b-gal DNA pol plasmid rep Operator plasmid DNA rep trans- Lactose permease acetylase plasmid O O plasmid – on the plasmid

Partial diploids: cis or trans-effect? 17 a. CA P Glucose - b-gal pol Oc mutation rep pol DNS P lac. I C E perm* transacetylase Oc lac. Z lac. Y- lac. A T Lactose - – on bacterial DNA DNS

Partial diploids: cis or trans-effect? 17 b. mutation pol repressor E C DNA P lac. I rep lac. Z- O CAP site entry site operator F plasmid T lac. A structural genes terminator transacetylase Glucose - P permease CA CA P b-gal* lac. Y b-gal pol rep Oc mutation rep pol DNA P lac. I Coli lac. Oc F’ lac. O+ C lac. Z+ lac. Z- E perm* transacetylase Oc lac. Z lac. Y- lac. A T lac. Y- -gal: continuously expressed lac. Y+ permease: only with lactose Lactose + – on bacterial DNA

Partial diploids: cis or trans-effect? 18. mutation C DNA P lac. I* repressor Orep E lac. Z CAP site entry site operator lac. Ystructural genes b-gal terminator transacetylase P rep pol b-gal* permease C E rep O lac. Z- Coli lac. I- lac. O+ lac. Z+ lac. Y- -gal F’ lac. O+ lac. Z- lac. Y+ permeáz lac I+ transacetylase I- mutation rep DNA P lac. I Glucose Lactose + CA CA P rep perm* DNA T lac. A lac. Y lac. A T with lactose – on bacterial DNA F plasmid