Download - Sintesis Protein Pada Eukariot 2012
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SINTESIS PROTEIN PADA
EUKARIOT
Evi Umayah Ulfa
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Type Location Substrate -amanitin
RNA Pol I Nucleoli Most rRNAs gene Insensitive
RNA Pol II Nucleo-plasm
All protein-codinggenes and some
snRNA genes
Verysensitive
RNA Pol III Nucleo-
plasm
tRNAs, 5S rRNA,
U6 snRNA andother small RNAs
Moderately
sensitive
Three eukaryotic polymerases
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TRANSCRIPTION INITIATION COMPLEX FORMATION
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5 CAP
The structure of the 5cap of
eukaryotic mRNAs.
From GTP
Initiating
nucleotide
The formation of the 5cap of
eukaryotic mRNAs.
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SPLICING
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Mechanisms Transesterification
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Translational control
Structure of eukaryotic and prokaryotic mRNAs:
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Faktor-faktor yang Terlibat
dalam Translasi
Inisiasi :
Kodon inisiasi : AUG
Aminoasil tRNA : Metionin
Eukaryot initiation factors (eIF) : eIF 1-6
Pemanjangan
Elongation Factor (EF)-Tu
Enzim peptidil transferase
EF-G
Terminasi Kodon terminasi (UAA, UGA, UAG)
eRF 1 dan 3
M d l f k i ib
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Model of eukaryotic ribosome
rRNAs are believed to play a catalytic role in protein
synthesis.
After removal of 95% of the ribosomal proteins, the
60S subunit can catalyze formation of peptide bonds.
Ribosomal proteins are now believed to help fold the
rRNAs properly and to position the tRNAs.
5 d ( ) d d t i iti ti
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The first step is the recognition of the 5 cap by eIF4F, which consists of three
proteins, eIF4E, eIF4G and eIF4A.
Cap binding protein, eIF4E, binds to cap
The N-terminus of eIF4G binds eIF4E and the C-terminus binds eIF4A
The 40S subunit binds to eIF4G via eIF3
5 end (cap) dependent initiation:
C D d t I iti ti f P t i S th i i E k t
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The 40S complex then scans
down the 5 untranslated region
to the first AUG codon.
A GTP hydrolysis step by eIF5
triggers GDP binding of eIF2
and release of initiation
proteins.
The 60S subunit joins the
complex and the 80S
ribosome initiates translate
the ORF.
An initiation complex forms at
the cap with the 40S ribosomal
subunit and other translation
initiation factors.
Cap-Dependent Initiation of Protein Synthesis in Eukaryotes
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Ribosome selects
aminoacylated tRNA
eEF1 and GTP are bound toaminoacylated tRNA
Ribosome catalyzes formationof a peptide bond
Translocation is dependent on
eEF2 and GTP hydrolysis
Many ribosomes may translate
mRNAs simultaneously on the
same strand.
Elongation
P A
eEF1
eEF2
GTP
GTP
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Termination
Translation is terminated
at one of three stop codons(UAA, UAG & UGA).
Termination codon at the
A site is recognized by the
release factor instead of atRNA
The release factor binds
the termination codon
The peptide chain is then
released followed by
dissociation of the tRNA
and the ribosome