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The lactose (lac) operon

The lactose (lac) operon. - a n example for prokaryotic gene regulation. 1. Nobel prize for the discovery of lac operon - 1965. Francois Jacob Jacques Monod. Pasteur Institute, Paris, France. 2. The structure of lac operon. E. coli DNA. operon. promoter. promoter.

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The lactose (lac) operon

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

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

  3. 2. The structure of lac operon E. coli DNA operon promoter promoter Structural genes E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site RNA pol operator structural genes terminator binding site catabolit activator protein binding site Cytoplasm cell wall outer world

  4. 3. Structure lac operon

  5. pol rep 4. Repression E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator rep: repressor pol: RNA polymerase

  6. rep 5. Induction E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator glucose galactose lactose rep: repressor pol: RNA polymerase

  7. permease b-gal pol trans- acetylase rep 5. Induction E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator rep: repressor pol: RNA polymerase

  8. CAP 6. Activation E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator CAP: catabolite activator protein cAMP No glucose

  9. CAP pol 6. Activation E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator cAMP No glucose

  10. permease CAP b-gal pol trans- acetylase 6. Activation E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator

  11. CAP pol 6. Activation E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator catabolite repression (endproduct inhibition) No cAMP Glucose is present

  12. Glucose - Lactose + permease CAP b-gal pol trans- acetylase rep adenylate cyclase cyclic AMP 7. Structure and operation of lac operon Combined regulation E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator lactose adenylate cyclase glucose lactose allolactose (inductor!) cAMP ATP

  13. Glucose - Lactose + CAP pol rep 8. Mutantbeta-gal E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator cAMP No glucose

  14. Glucose - Lactose + permease CAP b-gal* pol trans- acetylase 8. Mutantbeta-gal E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator lactose

  15. Glucose - Lactose + permease CAP b-gal pol rep 9. Transcription stop in genes stop E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator transcription stop

  16. Glucose - Lactose + CAP b-gal pol rep 9. Transcription stop in genes stop E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator

  17. Glucose - Lactose + CAP pol rep 9. Transcription stop in genes stop E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator

  18. Glucose - Lactose - permease CAP b-gal pol pol trans- acetylase rep 10. The Oc mutation of operon The operator is not able to bind the repressor E C P lacI lacY lacA DNA DNA lacZ T Oc repressor CAP site entry siteoperatorstructural genes terminator

  19. Glucose - Lactose - permease CAP b-gal pol pol trans- acetylase rep 11. The I- mutation of repressor The repressor is not able to bind to the operator E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator

  20. Glucose - Lactose + CAP pol pol rep 12. The Is mutation of repressor The repressor is unable to bind lactose E C P lacI* lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator

  21. Glucose - Lactose + CAP 13. Mutant CAP-I CAP is unable to bind cAMP E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator cAMP No glucose

  22. Glükóz - Laktóz + CAP pol 13. Mutant CAP-I CAP is unable to bind cAMP E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator cAMP No glucose

  23. Glucose + Lactose + permease CAP b-gal pol pol trans- acetylase rep 14. Mutant CAP-II CAP can bind promoter in the absence of cAMP E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator

  24. Glucose - Lactose + CAP pol rep rep rep rep rep rep rep rep 15. Too many repressors E C P lacI lacY lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator P plasmid lacI DNA P plasmid lacI DNA Repressor – on the plasmid P plasmid lacI DNA P plasmid lacI DNA

  25. Glucose - Lactose - permease CAP b-gal pol pol trans- acetylase rep rep rep 16. Too many operators E C P lacI lacY lacA DNA DNA lacZ T O represssor CAP site entry site operator structural genes terminator plasmid DNA O plasmid DNA O plasmid DNA O Operator – on the plasmid plasmid DNA O

  26. Glucose - Lactose - CAP perm* b-gal pol pol trans- acetylase rep 17a. Partial diploids: cis or trans-effect? Oc mutation – on bacterial DNA E C P lacI lacY- lacA DNS T DNS lacZ Oc

  27. Glucose - Lactose - Glucose - Lactose + permease CAP CAP b-gal* perm* b-gal pol pol pol pol trans- acetylase trans- acetylase rep rep rep 17b. Partial diploids: cis or trans-effect? mutation E C P lacI lacY lacA F plasmid DNA lacZ- T O repressor CAP site entry site operator structural genes terminator Oc mutation – on bacterial DNA E C P lacI lacY- lacA DNA T DNA lacZ Oc • ColilacOc lacZ+ lacY- -gal: continuously expressed • F’lacO+ lacZ- lacY+ permease: only with lactose

  28. Glucose - Lactose + Glucose - Lactose - permease CAP CAP b-gal* perm* b-gal pol pol trans- acetylase trans- acetylase rep rep rep rep rep rep 18. Partial diploids: cis or trans-effect? mutation E C P lacI* lacY- lacA DNA DNA lacZ T O repressor CAP site entry site operator structural genes terminator I- mutation – on bacterial DNA E C P lacI lacY lacA F plasmid T DNA lacZ- O • ColilacI- lacO+lacZ+lacY--galwith lactose • F’lac I+lacO+lacZ-lacY+ permeáz with lactose

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