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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