6 - Protein Synthesis and Tracking


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6 - Protein Synthesis and Tracking

  1. 1. Protein Synthesis & Trafficking<br />
  2. 2. Outline for Today<br />Protein Synthesis<br />Overview of Information Transfer<br />Transcription<br />Translation<br />Protein Trafficking<br />What goes where and why care?<br />Ribosome role <br />Pathway of secreted protein<br />
  3. 3. Fig. 4.10<br />Overview<br />
  4. 4. Overview<br />What is a gene?<br />Gene = sequence of nucleotides that codes for the synthesis of a piece of RNA<br />(simplified version)<br />http://library.thinkquest.org/19037/genome.html<br />
  5. 5. RNA<br />Ribonucleic acid<br />Types of RNA<br />mRNA (messenger RNA)<br />tRNA (transfer RNA)<br />rRNA (ribosomal RNA)<br />Overview<br />http://folding.stanford.edu/education/m.html<br />
  6. 6. mRNA<br />Patterned from DNA in the nucleus<br />Moves to the cytoplasm<br />10% of RNA is of this type<br />3 base sequence constitutes a codon<br />Overview<br />http://www.alumni.ca/~mcgo4s0/t3/RNA.html<br />
  7. 7. tRNA<br />Carries the amino acid from the cytoplasm to the ribosome<br />Anticodon is a recognition area <br />Complimentary to the codon of the mRNA<br />Specific for an amino acid<br />10% of the RNA is of this type<br />Fig. 4.8<br />Overview<br />
  8. 8. rRNA<br />The RNA portion of ribosomes<br />80% of RNA is of this type<br />Fig. 4.9<br />Overview<br />
  9. 9. Protein Synthesis<br />Overview<br />Information transfer<br />from nucleus to cytoplasm<br />Culminates in protein formation<br />
  10. 10. Stages<br />Two stages to protein synthesis<br />Transcription<br />Translation<br />Overview<br />3rd. Ed Fig. 4.6<br />
  11. 11. Stages<br />Transcription<br />DNA to mRNA code<br />Not all of the DNA is transcribed at once<br />Language of the nucleotides<br />Overview<br />http://ghs.gresham.k12.or.us/science/ps/sci/ibbio/chem/nucleic/chpt15/transcription.gif<br />
  12. 12. Stages<br />Translation<br />Translate the code from “A, C, G, and U” to amino acid language<br />Nucleic acid language to amino acid language<br />Overview<br />3rd. Ed Fig. 4.6<br />
  13. 13. Transcription<br />DNA to mRNA<br />nucleus<br />Stretch of DNA helix unwinds<br />RNA polymerase<br />DNA rules of complimentarity apply<br /> DNA RNA<br /> G C<br /> C G<br /> T A<br /> A U<br />Transcription<br />http://ghs.gresham.k12.or.us/science/ps/sci/ibbio/chem/nucleic/chpt15/transcription.gif<br />
  14. 14. Transcription<br />Separation of strands<br />Enzymes link nucleotides together based upon laws of complementarity<br />Russo, handout<br />
  15. 15. What are introns?(intervening regions)<br />Consider the following<br />inthebekweoitwoenasdfginninggodcreatedtheheavensdsjfaoiqwerjwqandtheearth<br />inthebekweoitwoenasdfginninggodcreatedtheheavensdsjfaoiqwerjwqandtheearth<br />inthebeginninggodcreatedtheheavensandtheearth<br />
  16. 16. mRNA Processing<br />Trans-Trans link<br />Don’t confuse introns and exons (expressed regions).<br />Finished mRNA<br />http://ghs.gresham.k12.or.us/science/ps/sci/ibbio/chem/nucleic/chpt15/intron.htm<br />
  17. 17. Translation<br />The Players!<br />Ribosome<br />Russo, handout<br />
  18. 18. Overview<br />mRNA leaves the nucleus and goes to the cytoplasm<br />Is recognized by the ribosomal subunit<br />Translation<br />Russo, handout<br />
  19. 19. Overview<br />Binding of subunits (amino acids) to get the polypeptide<br />Translation<br />Russo, handout<br />
  20. 20. Role of tRNA<br />“transfers” or carries the amino acid from the cytoplasm to the ribosome<br />Anti-codon<br />3 nucleotide base sequence<br />Complimentary to the codon<br />Translation<br />http://www.alumni.ca/~mcgo4s0/t3/RNA.html<br />
  21. 21. Codon<br />Triplet sequence on mRNA<br />1 codon codes for 1 amino acid<br />Remember this was coded from the DNA<br />Translation<br />Russo, handout<br />
  22. 22. Anticodon<br />Triplet sequence on tRNA<br />1 anticodon for a specific amino acid<br />Translation<br />Russo, handout<br />
  23. 23. All RNA’s involved<br />rRNA makes up the ribosome<br />tRNA brings the amino acid to the ribosome<br />mRNA carries the message from the nucleus (DNA)<br />The three types of RNA together carry out translation<br />Translation<br />http://www.cancerquest.org/index.cfm?page=45<br />
  24. 24. Let’s Watch a Video<br />https://paris.mcgraw-hill.com/sites/0073525693/student_view0/chapter4/how_translation_works.html<br />
  25. 25. Steps<br />Initiation<br />tRNA with amino acid binds to ribosome subunit<br />AUG is start codon<br />Therefore UAC is the anti-codon<br />Other subunit comes in<br />Another tRNA comes in with an aminio acid<br />Form the first peptide bond<br />Ribosome shifts a distance of 1 codon<br />How is the correct amino acid brought to the ribosome?<br />Translation<br />http://kvhs.nbed.nb.ca/gallant/biology/translation_initiation.jpg<br />
  26. 26. The genetic code<br />Translation<br />This lets you determine what amino acid is brought to the ribosome.<br />(read in mRNA)<br />Campbell et al., Fig. 10.11<br />
  27. 27. Steps<br />Elongation<br />Ribosome moves along the mRNA<br />Bond forms between 2 adjacent amino acids<br />Bond breaks between amino acid and tRNA<br />Process keeps going like a ticker tape<br />Translation<br />http://www.science.siu.edu/microbiology/micr302/figure%207.25.JPG<br />
  28. 28. Translation<br />Elongation = lengthening of peptide chain<br />Russo, handout<br />
  29. 29. Steps<br />Termination<br />The process stops because the protein is complete<br />Get one of the 3 stop codons<br />UAA<br />UAG<br />UGA<br />Translation<br />Campbell et al., Fig. 10.11<br />
  30. 30. Translation<br />Termination = addition of amino acids stops<br />Stop Codon =<br />Codon for which there is no<br />complementary anticodon<br />
  31. 31. Overview of the process<br />Campbell et al., Fig. 10.20<br />Translation<br />
  32. 32. Relationships<br />Fig. 4.10<br />Protein Synthesis<br />
  33. 33. = amino acid<br />Ribosome<br />Translation<br />mRNA message is “read” as triplet sequence <br />of nucleotides: CODON<br />
  34. 34. Mutations<br />Mutation is a change in the base of the DNA<br />At least one type of mutation is this type<br />(There are others that involve an addition or a deletion of a base<br />Sickle cell disease is caused by one change in the DNA bases resulting in an improper amino acid in the hemoglobin<br />A mistake at either transcription or translation can result in problems<br />Protein Synthesis<br />Campbell et al., Fig. 10.21<br />
  35. 35. Protein Trafficking<br />Fig. 4.11<br />
  36. 36. What goes where<br />Protein Trafficking<br />Way of determining what protein goes where in the cell<br />Tay-Sachs disease the proteins are supposed to go to the lysosome but they don’t<br />Get fatty acids accumulations<br />http://medgen.genetics.utah.edu/photographs/pages/tay.htm<br />http://www.dynagene.com/education/tay.html<br />
  37. 37. Ribosome location<br />Free ribosomes<br />Protein will stay in the cytoplasm or move to the nucleus or mitochondria<br />Stays in the cell<br />Anchored (to er)<br />Associated with the ER<br />Proteins destined for the plasma membrane , the lysosome,or released from the cell (secretion)<br />Fig. 3.26a<br />Protein Trafficking<br />Fig. 3.26b<br />
  38. 38. Pathway<br />Fig. 4.11<br />Protein Trafficking<br />Initial sequence of amino acids is a signal<br />Called the signal sequence<br />Signal is recognized by a particle in the cytoplasm<br />Signal recognition particle (SRP)<br />SRP pulls the complex to the endoplasmic reticulum<br />Signal peptide goes into the lumen of the ER<br />
  39. 39. Synthesis begins<br />Initial sequence of <br />amino acids is a <br />SIGNAL that directs <br />protein to<br /> the ER<br />whole protein threads<br />into the interior<br />of the ER<br />Signal sequence is<br />translocated across<br />membrane of the ER <br />to the inside<br />Protein Trafficking<br />“element” in cytoplasm<br />recognizes signal<br />and moves<br />whole complex to the<br />surface of the RER<br />RER<br />
  40. 40. Protein Trafficking<br />Inside the ER the signal sequence is cleaved<br />Can be altered in the ER<br />Remove some aa’s, folding, stabilizing with S-S bridges, adding carbs, etc.<br />Insulin starts out as 1 chain of 86 aa’s but ends up as 2 chains of 21 and 30 aa’s.<br />Protein put into a bud of the ER that forms a transport vesicle<br />Transport vesicle goes to the Golgi<br />Fuses with Golgi<br />Protein is liberated into the Golgi<br />Fig. 4.11<br />Protein Trafficking<br />
  41. 41. Completed protein<br />inside ER<br />Stimulus Applied<br />Immediate secretion<br />Regulated secretion<br />Protein Trafficking<br />RER<br />Signal<br />is removed<br />“budding”<br />Transport vesicle<br />“shuttle”<br />to Golgi<br />“budding”<br />Fusion with Golgi<br />Golgi<br />“modifications” occur<br />that provide sorting signals<br />“shuttle”<br />to membrane<br />Secretory vesicle<br />Storage vesicle<br />Fate #2<br />Fate #1<br />
  42. 42. Pathway<br />In the Golgi it is modified and sorted<br />Bud forms from the Golgi<br />Secretory vesicle<br />Leaves via exocytosis<br />Fig. 4.11<br />Protein Trafficking<br />
  43. 43. Pathway<br />Two possibilities for secretion<br />Immediate release<br />Regulated storage<br />Vesicles stay in cell for a while as storage vesicles<br />e.g. neurons and endocrine cells<br />Fig. 4.11<br />Protein Trafficking<br />
  44. 44. DNA<br />mRNA<br />mRNA<br />Signal <br />sequence<br />whole protein threads<br />into the interior<br />of the ER<br />Signal sequence is<br />translocated across<br />membrane of the ER <br />to the inside<br />Protein <br />Trafficking<br />Synthesis begins<br />Free ribosomal subunits <br />in the cytoplasm<br />Ribosome subunits <br />associate with mRNA<br />Initial sequence of <br />amino acids is a <br />SIGNAL that directs <br />protein to<br /> the ER<br />“element” in cytoplasm<br />recognizes signal<br />and moves<br />whole complex to the<br />surface of the RER<br />RER<br />
  45. 45. Eventually the protein <br />is moved into a membrane “bud” <br />which will generate a <br />transport vesicle<br />Transport vesicle<br />The transport vesicle <br />fuses with the Golgi and <br />releases the protein inside<br />Secretory vesicle<br />The ribosome dissociates <br />from the mRNA <br />RER<br />An enzyme inside the RER <br />will cleave off <br />the signal <br />sequence<br />The signal piece will be degraded; the remainder of the protein will be further processed<br />Protein is liberated into <br />the interior of the RER<br />once translation ends<br />After more processing, the protein <br />is moved into a membrane “bud” <br />which will generate a <br />secretory vesicle<br />The transport vesicle <br />shuttles the protein <br />to the Golgi<br />Golgi<br />
  46. 46. Storage vesicle<br />Plasma membrane<br />Plasma membrane<br />Secretory vesicle<br />Fate of the Secretory Vesicle<br />In some cases the secretory vesicle <br />will transition to the plasma membrane <br />for immediate secretion of the contents <br />into the extracellular space<br />Regulated Secretion requires that a stimulus<br />(trigger event) be applied to the cell to make the <br />storage vesicle release its contents <br />into the extracellular space<br />In some cells the vesicle can remain as a storage vesicle<br />for a period of time; <br />this is true in cells that have Regulated Secretion<br />STIMULUS!<br />Secretion into the extracellular space<br />Regulated secretion<br />