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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
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