Chapter 3 fundamentals of protein biochemistry

Protein Synthesis and Function: Chapter 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 Protein Translation tRNA  mRNA: template  Ribosomes: peptidyl transferase  tRNA: adaptors Acceptor end CCA terminus T loop T stem D stem Anticodon stem D loop Variable loop Anticodon loop Protein Translation  Amino-acyl tRNA synthetases specifically attach amino acids to tRNAs  amino acid + ATP aminoacyl-AMP + PPi  aminoacyl-AMP + tRNA aminoacyltRNA + AMP Protein Translation Protein Translation Protein Translation— Ter m ination  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 Initiation of Translation (Protein Synthesis) Attachment of Preinitiation Complex Protein Str ucture  Tertiary: further folding, loss of which denatures protein  Quaternary: protein–protein interaction for function Monomers form multimers  Dimer  Trimer  Tetramer Protein Function        Enzymes Transport Storage Motility Structural Defense Regulatory Conjugated Proteins    Lipoproteins–lipid Glycoproteins–carbohydrate Metalloproteins–metal atoms Non-amino acid portion–nonprotein prosthetic group MODIFICATION OF PROTEINS MODIFICATION OF PROTEINS MODIFICATION OF PROTEINS POST TRANSLATIONAL MODIFICATION OF PROTEINS PROCESSING OF INSULIN 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 Golgi Apparatus Golgi Apparatus Transpor t Process MULTIPLE CONTROL POINTS Summar y  Proteins are made of combinations of 20 amino acids  Protein structure and function depends on the amino acid content and organization  A gene is defined, in part, by an open reading frame that contains the genetic code  In the genetic code, three nucleotides code for each amino acid  Proteins are translated from mRNA by peptidyl transferase activity in the ribosome, using tRNA as adaptors [...]... joined together by -C-C-N- linkages or peptide bonds to make proteins Amino terminus Carboxy terminus INITIATION OF PROTEIN SYNTHESIS TRANSFER OF GROWING CHAIN Transfer Of Growing Chain Ter m ination Of Chain Location Of Translation Machiner y ENDOPLASMIC RETICULUM    Microscopic series of tunnels Involved in transport and storage Two types of ER:  Rough ER (RER)  Smooth ER (SER) ENDOPLASMIC RETICULUM...Scanning mRNA for AUG rRNA and Proteins of Ribosomes  Ribosomes are composed of both proteins and rRNA  Confer some of the specificity of these complex interactions Ribosomal Subunits Solving the Genetic Code  Four nucleotides must code for 20 amino acids  41 = 4, 42 = 16, 43 = 64, 44 = 256  George Gamow Solving the Genetic Code  Synthetic RNAs  ... 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 Smooth Endoplasmic Reticulum (SER)  Closed tubular network without ribosomes  Functions in  nutrient processing  synthesis and storage of lipids, etc Rough Endoplasmic... = pro-pro-pro AAAAAAAAA = lys-lys-lys  Marshall Nirenberg and Johann Matthaei Solving the Genetic Code  Synthetic RNAs of defined sequence  UCUCUC = ser-leu-ser-leu Gobind Khorana  Three nucleotides = 1 codon = 1 amino acid The Genetic Redundancy Wobble Code: And Str ucture of an Amino Acid Amino Acids Nonpolar Alanine, Ala, A Isoleucine, Ile, I Leucine, Leu, L Methionine, Met, M Phenylalanine,... pathway Smooth Endoplasmic Reticulum (SER)  Closed tubular network without ribosomes  Functions in  nutrient processing  synthesis and storage of lipids, etc Rough Endoplasmic Reticulum (RER) OVERVIEW OF SYNTHESIS POLYRIBOSOMES