details about protein syntesis

1. SAURAV SAHA
COLLEGE OF HORTICULLTURE
DEPERTMENT OF CPBMB
2014-11-106
4/19/2015 1

2. Translation
Conversion of mRNA base sequence into protein
amino acid base sequence is called translation. it
involved a stepwise reading of the message present in
mRNA base sequences in codon and translating into a
amino acid sequence in protein.
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3. Necessary material for the translation process
Amino acid
Ribosome
mRNA
t -RNA
 several translation factor
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4. About Ribosome
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5. 4

6. 6
StopStart
Polycisronic
Monocistronic
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7. mRNA
 The site where the ribosome bind is name Shine-
Dalgarno sequence.
 It is only present in a prokaryotic mRNA.
 Shine–Dalgarno sequence – The polypurine
sequence AGGAGG centered about 10 bp
before the AUG initiation codon on bacterial
mRNA.
 It is complementary to the sequence at the 3′ end of 16S
rRNA.
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8. Shine-Delgarno element
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9. Eukaryotic mRNA scanning
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10. About tRNA
The main important think
in tRNA structure is the
amino Acid acceptor
region and anticodon
region in the translation
process.
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11. Mechanism of Translation
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12. A U G G G C U U A A A G C A G U G C A C G U U
This is a molecule of messenger RNA.
It was made in the nucleus by transcription
from a DNA molecule.
mRNA molecule
codon
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13. A U G G G C U U A A A G C A G U G C A C G U U
.
ribosome
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14. A U G G G C U U A A A G C A G U G C A C G U U
It brings an amino acid to the first three
bases (codon) on the mRNA.
Amino acid
tRNA molecule
anticodon
U A C
A transfer RNA molecule arrives.
The three unpaired bases (anticodon) on
the tRNA link up with the codon.
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15. A U G G G C U U A A A G C A G U G C A C G U U
A peptide bond forms between the two
amino acids.
Peptide bond
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16. A U G G G C U U A A A G C A G U G C A C G U U
The first tRNA molecule releases its amino acid
and moves off into the cytoplasm.
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17. A U G G G C U U A A A G C A G U G C A C G U U
The ribosome moves along the mRNA to the
next codon.
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18. A U G G G C U U A A A G C A G U G C A C G U U
Another tRNA molecule brings the
next amino acid into place.
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19. A U G G G C U U A A A G C A G U G C A C G U U
The polypeptide chain gets longer.
The process continues.
This continues until a termination (stop)
codon is reached.
The polypeptide is then complete.
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20. Initiation in prokaryotic
For the initiation it require
 mRNA.
 The initiator tRNA.
 Three initiation factor(IF1,IF2, IF3).
 Large and small unit of ribosome .
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21. Initiation process in prokaryotic
 mRNA gets bind on smaller
subunit and IF1 and IF3 bind
to 30S subunit
 IF2 complexed with GTP then
bind to the small subunits,
forming a complex at RBS.
 The initiator tRNA can then bind
to the complex at the P site paired
with AUG codon.
 The 50S subunits can now
bind. GTP is then hydrolyzed
and IFs are released to give
the 70S initiation complex
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22. Elongation process
 An aminoacetyle-tRNA with EF-TU-GTP complex
binding in A site of ribosome.
 Then formation of peptide bond between two amino
acid with the help of peptidyl transferase enzyme
which is the function of the 50 s ribosome.
 Then after the peptide bond formation t-RNA released
from the p site.
 Then t-RNA from the A site moved to P site along with
the movement of corresponding m-RNA making A site
free for the new incorporation of aa-t-RNA, this
process called translocation and factor associate with
EF-G with GTP complex.
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23. 23

24. Termination
Termination is signalled by the three
termination codon (UAG, UAA,UGA)
and mediate by the release
factor(RF1,RF2,RF3) .
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25. Function of the different release factor
 RF1 or RF2 – The bacterial release factor that
recognizes UAA and UAG and UGA as signals to
terminate polypeptide translation.
 RF3-
It functions to release the factors RF1 or
RF2 from the ribosome when they act to
terminate polypeptide translation.
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26. FUNCTION OF DIFFERENT FACTOR IN PROKARYOTIC
TRANSLATION
Initiation factor
IF-1 prevent premature entry of the t-RNA into A site
IF-2 directs the initiator t-RNA to its correct position of the
initiation complex
IF-3 prevent pre mature association of the ribosome unit
Elongation factor
EF-TU direct the next t-RNA to its correct position in the
ribosome.
EF-TS regenerate the EF-TU factor
EF-G mediate the translocation
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27. Conti……
Release factor
RF-1 recognize the termination codon UAA, UAG
RF-2 recognize the UAA , UGA codon
RF-3 stimulate the dissociation of the Both the factor
Ribosomal recycling factor
RRF responsible for the dissociation of the ribosomal
subunit after translation has terminate
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28. Initiator
tRNA+eIF2+GTP
eIF3+40S
(Ternary
complex)
43S pre initiation complex
+mRNA+eIF4F+eI
F4B
ATP
ADP+Pi
48S pre initiation complex
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Initiation process in eukaryotic
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29. Scanning
More factors
involved
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30. Scanning to
find AUG
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31. Elongation in eukaryotic
Elongation same as prokaryotic but only difference is
the factor
The factors EF-Tu EF-Ts EF-G have direct eukaryotic
equivalents called eEF1α, eEF1βγ, eEF2.
Termination
Termination is also similar to the prokaryotic , but here only one release
factor
eRF instead of three release factor RF 1 RF 2 RF3
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32. Prokaryotic
factor
Eukaryotic factor Function
IF1
IF2
IF3
eIF1 eIF1A
eIF2 eIF2B
eIF3 eIF4C
eIF4A eIF4B, eIF4F
eIF5
Block the A site
Help to bind Met-tRNA
First to bind and prepare 40S for
subsequent factors
As eIF1 eIF1A
Help dissociate IF2, eIF3,
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Initiation factors
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33. 33
Elongation factors
Prokaryotic factor Eukaryotic
factor
Function
EF-Tu
EF-Ts
EF-G
eEF1α
eEF1βγ
eEF2
A delivery of Aminoacyl
tRNA to ribosome
Aiding the Recycling of
EF-Tu or eEF1α
Translocation
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34. 34
Termination factors
Prokaryotic factor Eukaryotic factor Function
RF1, RF2, RF3 eRF 1
Release of complex
polypeptide chain
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35. Comparison prokaryotic and eukaryotic translation
Prokaryotic Eukaryotic
It occur on 70S ribosome It occur on 80S ribosome
It is a continuous process both
transcription and translation occur in
cytoplasm
It is a discontinuous process both
transcription occur in nucleus and
translation in cytoplasm
mRNA polycistronic mRNA monocistronic
First amino acid taking part is fMet First amino acid taking part is Met
It is a first process 20 amino acid per
second
It is a slow process 6 amino acid per
second
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36. It require three initiation factor
IF1, IF2, IF3.
It require nine initiation factor
It require three release factor RF1 RF2 It require one release factor eRF 1
mRNA life is short few seconds to few
minutes
mRNA life span is few hour to few days
Cont……….
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