Protein Translation Notes PDF

1  2 PART II-B Genetic code Translation  3 “Every minute, each human cell constructs up to 7,500 ribosomes – essential intracellular factories that decode instructions from genes to make all the proteins in the body” Alan J. Warren...

1  2 PART II-B Genetic code Translation  3 “Every minute, each human cell constructs up to 7,500 ribosomes – essential intracellular factories that decode instructions from genes to make all the proteins in the body” Alan J. Warren, Nature News and Views, 02/26/2020  4 Characteristics of the Genetic Code 1. Triplet code 2. The code is specific 4. The code is degenerate 5. An initiation codon sets the reading frame (start signal) 6. The code is non-overlapping 7. Termination codons indicate the end of the coding sequence (stop signal) 8. The code is universal  5 In bacteria, translation occurs cotranscriptionally Expressome (transcription + translation machinery) Ribosome binding site on mRNA = Shine-Dalgarno sequence  6 Translation in Prokaryotes - Stages Initiation: Formation of 30S preinitiation complex (30S PIC) Formation of the 30S initiation complex (30S IC) Formation of the 70S initiation complex (70S IC) Elongation: Decoding Peptide bond formation Translocation Termination  7 Initiation: 30S PIC IF3, IF2 + GTP, and IF1 bind to 30S. IF2 recruits fMet-tRNAfMet  8 Initiation: 30S IC mRNA is recruited to 30S PIC.  9 Initiation: 70S IC 50S joins the 30S IC and triggers IF dissociation. fMet-tRNAfMet is placed in P site.  10 Elongation: Decoding, peptide bond formation, translocation Decoding  11 Translation termination RF1/2: Recognition of stop codon Hydrolysis of peptidyl-tRNA bond by ribosome RF3: Helps dissociate RF1/2 from the ribosome RRF and EF-G help separate 30S from 50S. tRNA is dissociated by IF3.  12 Protein structure  13 Posttranslational Modifications Covalent modifications to amino acids of a peptide. Change structure and chemical properties of peptide. Common post- translational modifications: trimming, phosphorylation, glycosylation, acetylation, methylation. Reversible/irreversible.  14 ADDITIONAL SLIDES  15 Structure of a tRNA 16  17 Chaperonins 1aon