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Protein Synthesis and Function: Chapter 3

Protein Synthesis and Function: Chapter 3. Central Dogma. Central Dogma of the transfer of biological information. DNA RNA protein. Nucleic acid sequence must be translated into an amino acid sequence. PROTEIN SYNTHESIS. tRNA. Acceptor end. CCA terminus. T loop. T stem. D stem.

henrietta-jordan
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Protein Synthesis and Function: Chapter 3

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  1. Protein Synthesis and Function: Chapter 3

  2. Central Dogma Central Dogma of the transfer of biological information. DNA RNA protein Nucleic acid sequence must be translated into an amino acid sequence.

  3. PROTEIN SYNTHESIS

  4. tRNA Acceptor end CCA terminus T loop T stem D stem D loop Anticodon stem Variable loop Anticodon loop Protein Translation • mRNA: template • Ribosomes: peptidyl transferase • tRNA: adaptors

  5. Protein Translation • Amino-acyl tRNA synthetases specifically attach amino acids to tRNAs. • amino acid + ATP aminoacyl-AMP + PPi • aminoacyl-AMP + tRNA aminoacyl-tRNA + AMP

  6. Protein Translation

  7. Protein Translation

  8. Protein Translation—Termination • Termination of the amino acid chain is signaled by one of three nonsense, or termination codons, UAA, UAG, or UGA which are not charged with an amino acid. • Termination or release factors trigger hydrolysis of the finished polypeptide from the final tRNA.

  9. Initiation of Translation (Protein Synthesis)

  10. Attachment of Preinitiation Complex

  11. Scanning mRNA for AUG

  12. rRNA and Proteins of Ribosomes • Ribosomes are composed of both proteins and rRNA • Confer some of the specificity of these complex interactions

  13. Ribosomal Subunits

  14. Solving the Genetic Code • Four nucleotides must code for 20 amino acids. • 41 = 4, 42 = 16, 43 = 64, 44 = 256 • George Gamow

  15. Solving the Genetic Code • Synthetic RNAs • UUUUUUUUU = phe-phe-phe • GGGGGGGGG = gly-gly-gly • CCCCCCCCC = pro-pro-pro • AAAAAAAAA = lys-lys-lys • Marshall Nirenberg and Johann Matthaei

  16. Solving the Genetic Code • Synthetic RNAs of defined sequence • UCUCUC = ser-leu-ser-leu Gobind Khorana • Three nucleotides = 1 codon = 1 amino acid

  17. The Genetic Code: Redundancy And Wobble

  18. Structure of an Amino Acid

  19. Nonpolar Alanine, Ala, A Isoleucine, Ile, I Leucine, Leu, L Methionine, Met, M Phenylalanine, Phe, F Tryptophan,Trp, W Valine, Val, V Negatively Charged (Acidic) Aspartic acid, Asp, D Glutamic acid, Glu, E Polar Asparagine, Asn, N Cysteine, Cys, C Glutamine, Gln, Q Glycine, Gly, G Proline, Pro, P Serine, Ser, S Threonine, Thr, T Tyrosine, Tyr, Y Positively Charged (Basic) Arginine, Arg, R Histidine, His, H Lysine, Lys, K Amino Acids

  20. Amino Acid Structures

  21. Isoelectric Point (pI) • Amino acids are neutral at a pH, which is their isoelectric point (pI).

  22. Peptide Bonds • Amino acids are joined together by -C-C-N- linkages or peptide bonds to make proteins.

  23. Amino terminus Carboxy terminus

  24. INITIATION OF PROTEIN SYNTHESIS

  25. TRANSFER OF GROWING CHAIN

  26. Transfer Of Growing Chain

  27. Termination Of Chain

  28. Location Of Translation Machinery

  29. ENDOPLASMIC RETICULUM • Microscopic series of tunnels • Involved in transport and storage • Two types of ER: • Rough ER (RER) • Smooth ER (SER)

  30. ENDOPLASMIC RETICULUM

  31. Rough endoplasmic reticulum (RER) • Originates from the outer membrane of the nuclear envelop • Extends in a continuous network through cytoplasm • Rough due to ribosomes • Proteins are synthesized and shunted into the ER for packaging and transport • First step in secretory pathway

  32. Smooth Endoplasmic Reticulum (SER) • Closed tubular network without ribosomes • Functions in • nutrient processing • synthesis and storage of lipids, etc.

  33. Rough Endoplasmic Reticulum (RER)

  34. OVERVIEW OF SYNTHESIS

  35. POLYRIBOSOMES

  36. Protein Structure • Primary: amino acid sequence • Secondary: Intra-chain folding • beta-pleated sheets • alpha helices

  37. Protein Structure • Four levels of structure • Primary • Secondary • Alpha helix, beta pleated sheet, random coil • Tertiary • Quatanary

  38. Primary Structure: Amino Acid Sequence

  39. Secondary Structure: Alpha Helix, Beta-pleated Sheet, or Random Coil

  40. Extracellular domains (charged, glycosylated) Cell membrane Transmembrane domains (hydrophobic) Intracellular domains (hydrophilic) Amino Acid Content Determines Protein Structure and Function.

  41. Protein Structure • Tertiary: further folding, loss of which denatures protein • Quaternary: protein–protein interaction for function. Monomers formmultimers. • Dimer • Trimer • Tetramer

  42. Protein Function • Enzymes • Transport • Storage • Motility • Structural • Defense • Regulatory

  43. Conjugated Proteins • Lipoproteins–lipid • Glycoproteins–carbohydrate • Metalloproteins–metal atomsNon-amino acid portion–nonprotein prosthetic group

  44. MODIFICATION OF PROTEINS

  45. MODIFICATION OF PROTEINS

  46. MODIFICATION OF PROTEINS

  47. POST TRANSLATIONAL MODIFICATION OF PROTEINS

  48. PROCESSING OF INSULIN

  49. Golgi Apparatus • Consists of a stack of flattened sacs called cisternae • Closely associated with ER • Transitional vesicles from the ER containing proteins go to the Golgi apparatus for modification and maturation • Condensing vesicles transport proteins to organelles or secretory proteins to the outside

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