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TRANSLATION

1. TRANSLATION. 2. TRANSLATION INTRODUCTION Protein (amino acid polymer, N terminus, C terminus Ribosomes: 30 S subunit plus 50 S subunit form functional 70 S ribosome mRNA is read 5' to 3' Initiation Codons; Stop Codons Polysomes INITIATION

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TRANSLATION

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  1. 1 TRANSLATION

  2. 2 TRANSLATION INTRODUCTION Protein (amino acid polymer, N terminus, C terminus Ribosomes: 30 S subunit plus 50 S subunit form functional 70 S ribosome mRNA is read 5' to 3' Initiation Codons; Stop Codons Polysomes INITIATION Initiator tRNA (N - formylmethionyltRNA) Initiation complex ELONGATION Peptidyltransferase A, P, E sites on ribosome TERMINATION Stop codons SHINE-DALGARNO

  3. 3 AMIDES AMINE ACID AMIDE MONO SUBSTITUTED DISUBSTITUTED PEPTIDE-AMIDE FORMED BETWEEN TWO AMINO ACIDS: ALANYL-GLYCINE PEPTIDE BOND

  4. 4 N C PROMOTER +1 GENE 5' 3' 3' 5' TRANSCRIPTION 5' 3' UNTRANSLATED REGION TRANSLATION CODE NOBEL HOLLEY NIRENBERG KHORANA [STOP CODONS = UAA/UAG/UGA]

  5. 5 RIBOSOMES - NON-SPECIFIC TRANSLATE ANY MESSAGE PROKARYOTIC 70S 50S + 30S SUBUNITS POLYSOMES

  6. 6 TRANSFER RNA tRNA ~ 60 EACH SPECIFIC FOR 1 AMINO ACID AND 1 CODON HO 3' 5' tRNAPHE SPECIFIC FOR PHENYLALANINE 3' 5' ANTICODON 5' 3' CODON FOR PHENYLALANINE mRNA tRNA - IS AN ADAPTER - ADAPTS AMINO ACID AND CODON

  7. 7 GENETIC CODE IS DEGENERATE - DIFFERENT TRIPLETS ENCODE THE SAME AMINO ACID ACA ACG ACC ACU ALL CODE THREONINE "WOBBLE" MEANS THAT SOME SPECIFIC tRNAs CAN READ MORE THAN ONE CODON A THREONINE tRNA WITH AN ANTI-CODON OF 3' UGG5' 5' ACC3' 5' ACU3' PAIRS WITH OR THREONINE "WOBBLE" MAKES IT POSSIBLE FOR AN ORGANISM TO TRANSLATE ALL 61 CODONS WITH FEWER THAN 61 tRNAs PROKARYOTES OFTEN HAVE 60 - 80 tRNAs SOME DIFFERENT tRNAs CARRY THE SAME AMINO ACIDS SOME HIGHLY SPECIALIZED PROKARYOTES HAVE ~ 40 tRNA GENES

  8. 8 AMINO ACID ACTIVATION – LINKING AMINO ACIDS TO tRNAs AMINO ACID + ATP + tRNA (SPECIFIC FOR THAT AMINO ACID) → AMINO ACYL-tRNA + AMP + PPi e.g., GLYCINE LINKED TO tRNA SPECIFIC FOR GLYCINE WITH GLYCINE ANTICODON

  9. 9 INITIATING TRANSLATION FORMYL METHIONINE~tRNA [SPECIFIC FOR STARTING TRANSLATION] METHIONINE + tRNAfMET + ATP + ACTIVATING ENZYME fMET fMET FORMYL GROUP [FOLIC ACID] N-FORMYL METHIONYL ~tRNAfMET METHIONYL tRNAfMET

  10. 10 F MET INITIATION COMPLEXES mRNA + 30S + F - MET~tRNAfMET + GTP + INITIATION PROTEINS 30S INITIATION COMPLEX 30S SUBUNIT 5' mRNA 3' pppG 50S SUBUNIT F MET 70S RIBOSOME 3' pppG E A P EXIT ACCEPTOR PEPTIDYL

  11. 11 ELONGATION-POLYMERIZATION F-MET SER 5' G 3' A P F-MET SER TYR 5' G 3' A P PEPTIDYL TRANSFERASE [CHLORAMPHENICOL]

  12. 12 F-MET HO SER TYR 3' 5' A P TRANSLOCATION [ERYTHROMYCIN – INHIBITS MOVEMENT AMINO ACYL TRNA FROM A SITE TO P SITE, BLOCKS ELONGATION; AZITHROMYCIN] F-MET HO SER TYR 3' 5' E A P

  13. 13 HO GLN F-MET SER TYR HO GUC 5' E A P TETRACYCLINE – INHIBITS AMINO ACYL TRNA BINDING A SITE DOXYCYCLINE - NEWER STREPTOMYCIN - TRNA MISMATCHING, MIS-TRANSLATION SPECTINOMYCIN - BINDS 30S SUBUNIT; EXACT MECHANISM ? ALL INHIBIT 30S RIBOSOME FUNCTION

  14. PEPTIDYL TRANSFERASE 14 PEPTIDYL TRANSFERASE UN-CHARGED tRNA PEPTIDYL ~ tRNA

  15. 15 HOW DO RIBOSOMES KNOW WHERE TO START TRANSLATING? A. HOW TO DISTINGUISH INITIAL AUG FROM INTERNAL AUG AUG AUG UAA 5' 3' PROTEIN CODING REGION UNTRANSLATED REGION INTERNAL AUG B. HOW TO RECOGNIZE SEVERAL INITIATING AUG's IN ONE mRNA AUG AUG AUG 5' 3' 1st CODING REGION 2nd CODING REGION 3rd CODING REGION POLY CISTRONIC mRNA RIBOSOMES TRANSLATE ALL THREE INDEPENDENTLY. HOW?

  16. 16 SHINE DALGARNO SHINE DALGARNO AUG AUG 5' 3' CODING REGION CODING REGION PROTEIN CODING REGIONS ARE PRECEDED BY SHINE-DALGARNO SEQUENCES [PROKARYOTES] SHINE DALGARNO SEQUENCES: ~ 7 +1 5' SHINE DALGARNO

  17. 17 BINDING BETWEEN SHINE-DALGARNO AND rRNA (16S) POSITIONS mRNA SO THAT AUG OCCUPIES P SITE 30S SUBUNIT SITES

  18. 18 REPLICATION, TRANSCRIPTION & TRANSLATION - DYNAMIC mRNA RIBOSOMES PROTEINS THEY ALL GO ON AT THE SAME TIME !

  19. RIBOSOMES ARE RIBOZYMES - THE ACTIVE SITE FOR CATALYZING PEPTIDE BOND FORMATION IS ENTIRELY RNA 23S rRNA IS PEPTIDYL TRANSFERASE ADENINE [#2451] PARTICIPATES IN FORMING PEPTIDE BONDS 19 CHLORAMPHENICOL BINDS A 2451 & A 2452 - INHIBITS ADENINE #2451 APPRECIATE ! H BOND ADENINE N3 TAKES PROTON NITROGEN ATTACKS

  20. 20 H BOND STABILIZES INTERMEDIATE tRNA OXYGEN TAKES PROTON tRNA PEPTIDE BOND BREAKS OXYANION ELECTRONS FORM C O APPRECIATE !

  21. 21 PEPTIDE BOND FORMS APPRECIATE ! GROWING PEPTIDE HAS BEEN ADDED TO ONE MORE AMINO ACID OR; ONE MORE AMINO ACID HAS BEEN ADDED TO GROWING PEPTIDE ADENINE #2451 IS NOW READY TO REPEAT THE PROCESS

  22. TAKE AWAY: AMINO ACID STRUCTURE, FUNCTIONAL GROUPS, HOW THEY REACT TO FORM PROTEINS? WHAT IS GENE EXPRESSION AND HOW IS GENETIC INFO USED? RIBOSOMES, tRNAs, GENETIC CODE, AMINO ACID ACTIVATION – STRUCTURES, HOW THEY FUNCTION, WHAT IS ACCOMPLISHED? POLYMERIZATION – INITIATION, ELONGATION, PEPTIDYL TRANSFERASE, STEPS? SHINE DALGARNO – STRUCTURE, FUNCTION, HOW FUNCTION IS PERFORMED?

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