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PROTEIN PROTEIN SYNTHESISSYNTHESIS
Used and Modified with permission from Used and Modified with permission from
Robert GoodmanRobert Goodman, , Biology Department,Citrus Community CollegeBiology Department,Citrus Community College
Protein SynthesisProtein Synthesis• The production (synthesis) of proteinsproteins.
• 3 phases3 phases:
1.1. TranscriptionTranscription
2.2. RNA processingRNA processing
3.3. TranslationTranslation
• Remember: Remember: DNA DNA RNA RNA ProteinProtein
DNA DNA RNA RNA ProteinProtein
Nuclearmembrane
TranscriptionTranscription
RNA ProcessingRNA Processing
TranslationTranslation
DNA
Pre-mRNA
mRNA
Ribosome
Protein
Eukaryotic Eukaryotic CellCell
TranscriptionTranscription
TranslationTranslation
DNA
mRNA
Ribosome
Protein
Prokaryotic CellProkaryotic Cell
DNA DNA RNA RNA ProteinProtein
Question:Question:
How does RNARNA (ribonucleic acid) (ribonucleic acid) differ
from DNA DNA (deoxyribonucleic acid)(deoxyribonucleic acid)?
RNARNA differs from differs from DNADNA1. RNARNA has a sugar ribosesugar ribose
DNADNA has a sugar deoxyribosesugar deoxyribose
2. RNARNA contains uracil (U)uracil (U)
DNADNA has thymine (T)thymine (T)
3. RNARNA molecule is single-strandedsingle-stranded
DNADNA is double-strandeddouble-stranded
1. Transcription1. Transcription
Nuclearmembrane
TranscriptionTranscription
RNA ProcessingRNA Processing
TranslationTranslation
DNA
Pre-mRNA
mRNA
Ribosome
Protein
Eukaryotic Eukaryotic CellCell
1. Transcription1. Transcription• The transfer of information in the
nucleusnucleus from a DNADNA molecule to an RNARNA molecule.
• Only 1 1 DNADNA strand serves as the templatetemplate
• Starts at promoter DNADNA (TATA box)• Ends at terminator DNADNA (stop)• When complete, pre-RNApre-RNA molecule is
released.
Question:Question:
• What is the What is the enzymeenzyme responsible for the responsible for the production of the RNA production of the RNA molecule?molecule?
Answer:Answer: RNA Polymerase RNA Polymerase• Separates the DNADNA molecule by
breaking the H-bonds between the bases.
• Then moves along one of the DNA DNA strandsstrands and links RNARNA nucleotides together.
1. Transcription1. Transcription
DNADNA
pre-mRNApre-mRNA
RNA PolymeraseRNA Polymerase
Question:Question:• What would be the complementary
RNARNA strand for the following DNADNA sequence?
• DNA 5’-GCGTATG-3’DNA 5’-GCGTATG-3’
Answer:Answer:
• DNA 5’-GCGTATG-3’DNA 5’-GCGTATG-3’
• RNA 3’-CGCAUAC-5’RNA 3’-CGCAUAC-5’
2. RNA Processing2. RNA Processing
Nuclearmembrane
TranscriptionTranscription
RNA ProcessingRNA Processing
TranslationTranslation
DNA
Pre-mRNA
mRNA
Ribosome
Protein
Eukaryotic Eukaryotic CellCell
2. RNA Processing2. RNA Processing• Maturation of pre-RNApre-RNA molecules.
• Also occurs in the nucleus.nucleus.
• IntronsIntrons spliced out by splicesome-splicesome-enzymeenzyme and exonsexons come together.
• End product is a mature RNA mature RNA moleculemolecule that leaves the nucleusnucleus to the cytoplasm.cytoplasm.
2. RNA Processing2. RNA Processing
pre-RNA molecule
intron
intronexon exon exon
exon exon exon
Mature RNA moleculeMature RNA molecule
exon exon exon
intron intron
splicesome splicesome
Types of RNATypes of RNA• Three types ofThree types of RNARNA:
A.A. messenger RNA (mRNA)messenger RNA (mRNA)
B.B. transfer RNA (tRNA)transfer RNA (tRNA)
C.C. ribosome RNA (rRNA)ribosome RNA (rRNA)
• Remember: all produced in theRemember: all produced in the nucleusnucleus!!
A. Messenger RNA (mRNA)A. Messenger RNA (mRNA)• Carries the information for a specific
proteinprotein.
• Made up of 500 to 1000 nucleotides nucleotides long.
• Made up of codons codons (sequence of three bases: AUG - methionine).
• Each codoncodon, is specific for an amino amino acidacid.
A. Messenger RNA (mRNA)A. Messenger RNA (mRNA)
methionine glycine serine isoleucine glycine alanine stopcodon
proteinprotein
A U G G G C U C C A U C G G C G C A U A AmRNAmRNA
startcodon
Primary structure of a proteinPrimary structure of a protein
aa1 aa2 aa3 aa4 aa5 aa6
peptide bonds
codon 2 codon 3 codon 4 codon 5 codon 6 codon 7codon 1
B. Transfer RNA (tRNA)B. Transfer RNA (tRNA)• Made up of 75 to 80 nucleotides long.
• Picks up the appropriate amino acid amino acid floating in the cytoplasm (amino acid amino acid activating enzymeactivating enzyme)
• Transports amino acids amino acids to the mRNAmRNA.
• Have anticodonsanticodons that are complementary to mRNAmRNA codonscodons.
• Recognizes the appropriate codonscodons on the mRNAmRNA and bonds to them with H-bonds.
B. Transfer RNA (tRNA)B. Transfer RNA (tRNA)
amino acidamino acidattachment siteattachment site
U A C
anticodonanticodon
methionine amino acidamino acid
C. Ribosomal RNA (rRNA)C. Ribosomal RNA (rRNA)• Made up of rRNArRNA is 100 to 3000
nucleotides long.
• Important structural component of a ribosome.ribosome.
• Associates with proteins proteins to form ribosomes.ribosomes.
RibosomesRibosomes• Large and small subunits.Large and small subunits.
• Composed of rRNA (40%) rRNA (40%) and proteins proteins (60%).(60%).
• Both units come together and help bind the mRNAmRNA and tRNA.tRNA.
• Two sites forTwo sites for tRNAtRNA
a. P siteP site (first and last tRNA will attachtRNA will attach)
b. A siteA site
RibosomesRibosomes
PSite
ASite
Largesubunit
Small subunit
mRNAmRNA
A U G C U A C U U C G
3. Translation3. Translation
Nuclearmembrane
TranscriptionTranscription
RNA ProcessingRNA Processing
TranslationTranslation
DNA
Pre-mRNA
mRNA
Ribosome
Protein
Eukaryotic Eukaryotic CellCell
3. Translation3. Translation• Synthesis of proteinsproteins in the
cytoplasmcytoplasm
• Involves the following:Involves the following:1. mRNA (codons)mRNA (codons)2. tRNA (anticodons)tRNA (anticodons)3. rRNArRNA4. ribosomesribosomes5. amino acidsamino acids
3. Translation3. Translation• Three parts:
1. initiationinitiation: start codon (AUG)
2. elongationelongation:
3. terminationtermination: stop codon (UAG)
• Let’s make a PROTEIN!!!!PROTEIN!!!!.
3. Translation3. Translation
PSite
ASite
Largesubunit
Small subunit
mRNAmRNA
A U G C U A C U U C G
InitiationInitiation
mRNAmRNA
A U G C U A C U U C G
2-tRNA
G
aa2
A U
A
1-tRNA
U A C
aa1
anticodon
hydrogenbonds codon
mRNAmRNA
A U G C U A C U U C G
1-tRNA 2-tRNA
U A C G
aa1 aa2
A UA
anticodon
hydrogenbonds codon
peptide bond
3-tRNA
G A A
aa3
ElongationElongation
mRNAmRNA
A U G C U A C U U C G
1-tRNA
2-tRNA
U A C
G
aa1
aa2
A UA
peptide bond
3-tRNA
G A A
aa3
Ribosomes move over one codon
(leaves)
mRNAmRNA
A U G C U A C U U C G
2-tRNA
G
aa1
aa2
A UA
peptide bonds
3-tRNA
G A A
aa3
4-tRNA
G C U
aa4
A C U
mRNAmRNA
A U G C U A C U U C G
2-tRNA
G
aa1aa2
A U
A
peptide bonds
3-tRNA
G A A
aa3
4-tRNA
G C U
aa4
A C U
(leaves)
Ribosomes move over one codon
mRNAmRNA
G C U A C U U C G
aa1aa2
A
peptide bonds
3-tRNA
G A A
aa3
4-tRNA
G C U
aa4
A C U
U G A
5-tRNA
aa5
mRNAmRNA
G C U A C U U C G
aa1aa2
A
peptide bonds
3-tRNA
G A A
aa3
4-tRNA
G C U
aa4
A C U
U G A
5-tRNA
aa5
Ribosomes move over one codon
mRNAmRNA
A C A U G U
aa1
aa2
U
primaryprimarystructurestructureof a proteinof a protein
aa3
200-tRNA
aa4
U A G
aa5
C U
aa200
aa199
terminatorterminator or stopor stop codoncodon
TerminationTermination
End ProductEnd Product• The end products of protein synthesis
is a primary structure of a proteinprimary structure of a protein.
• A sequence of amino acid amino acid bonded together by peptide bondspeptide bonds.
aa1
aa2 aa3 aa4aa5
aa200
aa199
PolyribosomePolyribosome• Groups of ribosomes reading same
mRNA mRNA simultaneously producing many proteins (polypeptides).proteins (polypeptides).
incominglargesubunit
incomingsmall subunit polypeptidepolypeptide
mRNAmRNA1 2 3 4 5 6 7
Question:Question:• The anticodon The anticodon UACUAC belongs to belongs to
a a tRNAtRNA that recognizes and that recognizes and binds to a particular binds to a particular amino amino acidacid..
• What would be the What would be the DNA base DNA base code code for this for this amino acid?amino acid?
Answer:Answer:• tRNA - UAC (anticodon)tRNA - UAC (anticodon)
• mRNA - AUG (codon)mRNA - AUG (codon)
• DNA - TACDNA - TAC