Chapter 4 – Protein Structure & RNA Translation (ProteinProduction)Part 1: Protein StructureI. Amino Acids A. Monomers with tetrahedral structure (fig. 4.1) B. 20 different onesC. Amino acids linked buy forming a peptide bond via dehydration (fig.4.3) II. Primary structure : AA chainIII. Secondary Structure : repeating folding patterns stabilized by H-bondsbetween a carbonyl group of 1 AA & amide group of anotherA. R groups not involvedB. Alpha helix: each carbonyl group H-bonds with an amide group 4amino acids ahead in the chain (fig. 4.6) C. Beta (pleated) sheet: the polypeptide folds back on itself and H bondsform between carbonyl groups in 1 chain and amide groups in theother chain (fig. 4.7)IV. Tertiary structure : polypeptide folds into a 3D shape becauseof R-group interactions A. Can be final structure but not alwaysV. Quaternary structure : 2+ polypeptides associate to form afunctional multimeric proteinA. Subunits of proteins with quat. structure may be identical ordifferent from each otherPart 2: TranslationI. Translation: mRNA protein A. 3 bases = 1 codon1. Sequence of bases in a codon specifies an amino acid, an amino acid AND start, or stop2. Each base only part of 1 codon (code doesn’t overlap)II. Equipment required for translation A. mRNA (fig. 3.22) (not here)1. introns/exons, poly-A tail2. 3’ end = poly-A tail; 5’ end = 5’ capB. Ribosome1. Complexes of protein & rRNA that form the environment for translation2. Looks like hamburger buna. When mRNA comes in, the large & small subunits of ribosome cometogether around strand of mRNAC. tRNA1. Brings specific AA to the ribosome2. Ensures the right AA gets matched to the right codon3. Structurea. Entire thing is single strand, but mostly folded over on itself and twisted to look likeribbon modelb. Top – single stranded – where amino acid attachesc. Bottom – 3 bases called “anticodon”i. Opposite in polarity & complementary to the mRNA4. To pick up an amino acid, tRNA interacts with a specific type of enzyme, forming “charged” tRNA (holding covalently bonded AA)5. Fig. 4.14 – AA attaches at small top part D. Sets of proteins1. Proteins to help start translation (initiation factors), keep it going (elongation factors), or end it (release factors)III. 3 stages if translation A. Initiation 1. Initiation factors bring the equipment for translationtogether2. Don’t know order (fig. 4.17 a & b) – just know how itall comes together B. Elongation1. Ribosome moves down mRNA as amino acids are addedto the polypeptide2. Starts at 5’ end & ribosome moves towards 3’ end (ofmRNA)3. Fig 4.15 great – base pairing occurs between the tRNA & mRNA codonC. Termination1. At stop codon, protein release factor binds to ribosome, breaking bond between the last tRNA & the polypeptideIV. Gene Expression A. Making a product from a geneB. Genes that code for RNA products: runtranscription (mRNA final product)C. Genes that code for proteins: runtranscription, then translationV. See end of chapter 4 – pages 4-16 &
View Full Document
Unlocking...