1 Protein Synthesis Computer Filename: Protsyna.ppt Material for Introductory Microbiology.

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Protein SynthesisProtein Synthesis

Computer Filename: Protsyna.pptComputer Filename: Protsyna.ppt

Material for Introductory Microbiology

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OverviewOverview

Genes are composed of DNA within Genes are composed of DNA within the chromosomethe chromosome

Genes code for proteinsGenes code for proteinsDNA is transcripted into RNADNA is transcripted into RNARNA is translated into protein by RNA is translated into protein by

ribosomesribosomesGenes regulated by control of RNA Genes regulated by control of RNA

productionproduction

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Lecture OutlineLecture Outline

tRNA structuretRNA structure adding amino acids to tRNAadding amino acids to tRNAribosome structureribosome structureribosome attachmentribosome attachmentprotein synthesis :initiation, elongation, protein synthesis :initiation, elongation,

attachmentattachment

Protein synthesisProtein synthesis

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Concepts from OACConcepts from OAC

Structure & Function of DNA & Structure & Function of DNA & RNARNA

Genetic codeGenetic codeTranscription & translationTranscription & translationProtein synthesisProtein synthesis

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Background Terms & ConceptsBackground Terms & Concepts

Structure of DNA & RNA Structure of DNA & RNA Ribosomes Ribosomes Enzymes Enzymes

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CODONSCODONS

sequences of three adjacent nucleotides that sequences of three adjacent nucleotides that code for one amino acid or polypetide code for one amino acid or polypetide terminationtermination

64 codons encrypt of ~ 20 amino acids64 codons encrypt of ~ 20 amino acids degenerate ACU, ACC,ACA, ACG degenerate ACU, ACC,ACA, ACG

threoninethreonine Start codon AUG (also codes for Start codon AUG (also codes for

methionine)methionine) Stop codon UAA,UAG,UGA (nonsense Stop codon UAA,UAG,UGA (nonsense

codons)codons)

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Interpreting the Genetic CodeInterpreting the Genetic Code

Two step process :Transcription -Two step process :Transcription -translationtranslation

Transcription DNA --> RNATranscription DNA --> RNA Translation RNA--> proteinTranslation RNA--> protein

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TranscriptionTranscription

occurs in nucleusoccurs in nucleus DNA unravels- single strandDNA unravels- single strand RNA Polymerase binds to Promotor siteRNA Polymerase binds to Promotor site Reads to stop codonReads to stop codon assembles complementary single strand of assembles complementary single strand of

RNA (primary RNA)RNA (primary RNA) Disengages when reaches stop codonDisengages when reaches stop codon

Production of an RNA copy of the geneProduction of an RNA copy of the gene

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Ribosomal RNARibosomal RNA

called rRNAcalled rRNA found in Ribosomesfound in Ribosomes catalytic sitecatalytic site provides site for protein provides site for protein

assemblyassembly ribosomal structure ribosomal structure

different in eukaryotes different in eukaryotes and prokaryotesand prokaryotes

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Prokaryotic ribosomeProkaryotic ribosome

70S 70S large ribosomal subunit 50S 1,600,000large ribosomal subunit 50S 1,600,000

34 proteins34 proteins

5S RNA 120 nucleotides5S RNA 120 nucleotides

23S RNA 2900 nucleotides23S RNA 2900 nucleotides Small ribosomal subunit 30S 900,000Small ribosomal subunit 30S 900,000

21 proteins21 proteins

16s RNA 1540 nucleotides16s RNA 1540 nucleotides

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Eukaryotic ribosomeEukaryotic ribosome

80 S 4,200,00080 S 4,200,000 large subunit 60S 2,800,000large subunit 60S 2,800,000

49 proteins49 proteins

5s RNA 120 nucleotides5s RNA 120 nucleotides

28s RNA 4700 nuclotides28s RNA 4700 nuclotides

5.8 s RNA 160 nuclotides5.8 s RNA 160 nuclotides Small subunit 40S 1,400,000Small subunit 40S 1,400,000

33 proteins33 proteins

18s RNA 1900 nuclotides18s RNA 1900 nuclotides

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Transfer RNATransfer RNA

called tRNAcalled tRNASmaller than mRNA or rRNASmaller than mRNA or rRNAfound in cytoplasmfound in cytoplasm40 different kinds of tRNA40 different kinds of tRNAtransports amino acids to ribosometransports amino acids to ribosomepositions amino acids on elongating positions amino acids on elongating

polypeptidepolypeptide

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tRNAtRNA

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tRNAtRNA

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tRNA Activating EnzymestRNA Activating Enzymes

Specific for each type of tRNASpecific for each type of tRNA called tRNA synthetasecalled tRNA synthetase binds to specific amino acidbinds to specific amino acid binds to specific nucleotides in tRNAbinds to specific nucleotides in tRNA covalently crosslinks amino acid to free 0Hcovalently crosslinks amino acid to free 0H water is lostwater is lost

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Large Ribosomal SubunitLarge Ribosomal Subunit

Two Two tRNA tRNA binding binding sitessites

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PolysomesPolysomes

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Ribosomes on Rough ERRibosomes on Rough ER

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EM of RibosomesEM of Ribosomes

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Protein SynthesisProtein Synthesis

Formation of an initiation Formation of an initiation complexcomplex

Chain elongationChain elongationChain terminationChain termination

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Concept Map:Protein SynthesisConcept Map:Protein Synthesis

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Initiation of Protein SynthesisInitiation of Protein Synthesis

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Initiation 2Initiation 2

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Initiation 3Initiation 3

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Initiation 4Initiation 4

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Internal Ribosome Entry SequencesInternal Ribosome Entry Sequences

PicroRNA viruses cleave eIF4gPicroRNA viruses cleave eIF4g and use IRESand use IRES