11 trp operon-2010 update

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11 trp operon-2010 update

  1. 2. trp Operon <ul><li>trp – tr y p tophan </li></ul><ul><li>The genes of the trp operon are used to make the amino acid tryptophan. </li></ul><ul><li>It is turned off when enough tryptophan is in the cell. </li></ul><ul><li>Tryptophan is the effector molecule. </li></ul>
  2. 3. trp Operon <ul><li>Operon codes for 5 genes – found in E. coli </li></ul><ul><li>Five polypeptides combine to make three enzymes . </li></ul><ul><ul><li>each enzyme participates in a step to make tryptophan </li></ul></ul>
  3. 4. Repressor Protein <ul><li>repressor protein ( trpR ) </li></ul><ul><ul><li>binds to operator when tryptophan is present. </li></ul></ul><ul><ul><li>prevents RNA polymerase from transcribing genes when bound to operator </li></ul></ul><ul><ul><li>transcribed as a different gene from trp operon </li></ul></ul><ul><li>When do you want the repressor to bind / not bind to the trp operon? </li></ul>
  4. 5. <ul><li>When tryptophan needs to be made: </li></ul><ul><ul><li>enzymes are required to make tryptophan </li></ul></ul><ul><ul><li>repressor is NOT bound to operator </li></ul></ul><ul><ul><li>transcription can proceed </li></ul></ul>
  5. 6. <ul><li>When cell has enough tryptophan: </li></ul><ul><ul><li>tryptophan binds to repressor </li></ul></ul><ul><ul><li>repressor can now bind operator to prevent transcription </li></ul></ul>
  6. 7. Effector Molecule <ul><li>Since tryptophan is the molecule that determines when the operon is turned on or off, it is known as an effector molecule. </li></ul><ul><li>corepressor – effector molecule that binds repressor protein to cause it to bind to the operator </li></ul>
  7. 10. trp Operon <ul><li>trp – tr y p tophan </li></ul><ul><li>The genes of the trp operon are used to make the amino acid tryptophan. </li></ul><ul><li>It is turned off when enough tryptophan is in the cell. </li></ul><ul><li>Tryptophan is the effector molecule. </li></ul>
  8. 11. trp Operon <ul><li>Operon codes for 5 genes – found in E. coli </li></ul><ul><li>Five polypeptides combine to make three enzymes . </li></ul><ul><ul><li>each enzyme participates in a step to make tryptophan </li></ul></ul>
  9. 12. Repressor Protein <ul><li>repressor protein ( trpR ) </li></ul><ul><ul><li>binds to operator when tryptophan is present </li></ul></ul><ul><ul><li>prevents RNA polymerase from transcribing genes when bound to operator </li></ul></ul><ul><ul><li>transcribed as a different gene from trp operon </li></ul></ul><ul><li>When do you want the repressor to bind / not bind to the trp operon? </li></ul>
  10. 13. <ul><li>When tryptophan needs to be made: </li></ul><ul><ul><li>enzymes are required to make tryptophan </li></ul></ul><ul><ul><li>repressor is NOT bound to operator </li></ul></ul><ul><ul><li>transcription can proceed </li></ul></ul>
  11. 14. <ul><li>When cell has enough tryptophan: </li></ul><ul><ul><li>tryptophan binds to repressor </li></ul></ul><ul><ul><li>repressor can now bind operator to prevent transcription </li></ul></ul>
  12. 15. Effector Molecule <ul><li>Since tryptophan is the molecule that determines when the operon is turned on or off, it is known as an effector molecule. </li></ul><ul><li>corepressor – effector molecule that binds repressor protein to cause it to bind to the operator </li></ul>

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