Introduction. History. Central dogma. Mechanism of protein synthesis. Transcription. Process of transcription translation Step of translation Activation of amino acid. Transfer of amino acid to tRNA. Initiation of polypeptide chain Elongation of polypeptide chain Translocation Termination of polypeptide chain processing of released polypeptide chain Main difference between protein synthesis in prokaryotes and eukryotes Conclusion Reference

1. PROTEINSYNTHESIS IN EUKARYOTES
By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

2. SYNAPSIS
• Introduction.
• History.
• Central dogma.
• Mechanism of protein synthesis.
1. Transcription.
• Process of transcription
2. translation
• Step of translation
• Activation of amino acid.
• Transfer of amino acid to tRNA.
• Initiation of polypeptide chain
• Elongation of polypeptide chain
• Translocation
• Termination of polypeptide chain
• processing of released polypeptide chain
• Main difference between protein synthesis in prokaryotes and eukryotes
• Conclusion
• Reference

3. INTRODUTION
• Protein is biological macromolecules
such as polysaccharides and nucleic acids,
• proteins are essential parts of living
organisms and participate in virtually
every process within cells.
• Many proteins are enzymes that
catalyze biochemical reactions and
are vital to metabolism.
• Proteins also have structural or
• mechanical functions, such as actin and myosin in
muscle and the proteins in the cytoskeleton, which form
a system of scaffolding that maintains cell shape

4. HISTORY
• Proteins were first described by the Dutch
chemist Gerhardus Johannes Mulder and
named by the Swedish chemist JONS JAKOB
BERZELIUS in 1838.
• CRICK proposed the central dogma.
• BRENNER ,JACOB,and MASELSON
demonstrate the function of mRNA.
• HALL and SPIEGELMAN obtain direct evidence
that the mRNA molecule is formed on one DNA
template strand.

5. CENTRAL DOGMA
• “Central dogma of molecular genetics is the
undirectional flow of genetic informations from
DNA to DNA or DNA to RNA and RNA to
PROTEIN.
• Central Dogma involves in the following steps:
1. Transcription.
2. Translation.
DNA mRNA PROTEIN
DNA

6. MECHANISM OF PROTEIN
SYNTHESIS
transcription
• Transcription is the “copying of complementory
messenger RNA strand on DNA strand.”
DNA mRNA.
• Transcription process involves an enzyme called RNA
polymerase which attaches with DNA strand and
unwind the two strands at a specific point.
• In eukryotes ,there are 3 different types of RNA
polymerase which synthesis various types of RNA.
1. RNA polymerase I : for rRNA synthesis.
2. RNA polymerase II: for mRNA synthesis.
3. RNA polymerase III: for tRNA synthesis.

7. RNA POLYMERASE

8. PROCESS OF TRANSCRIPTION
• Core enzyme and sigma joint to from RNA polymerase
enzyme.
• RNA polymerase attaches to initiation site.
• DNA unwinds and core enzyme catalysis of mRNA and
sigma factor get dissociate from the core enzyme.
• The mRNA chain grows longer.
• Termination of mRNA chain growth at termination site by
rho-factor.
• During trascription Adenine(A) picks up Uresil(U)
because there is no Thymine(T) in mRNA.and
• Every Guanine(G) picks up Cytosine(C).

10. TRANSLATION
• “It is a process in which genetic
information present in mRNA are translate
into the language of protein”.
• mRNA protein

11. TRANSLATION PROCESS

12. Nuclear
membrane
Transcription
RNA Processing
Translation
DNA
Pre-mRNA
mRNA
Ribosome
Protein
Eukaryotic Cell
Eukaryotic
Cell
DNA  RNA  Protein

13. Steps of translation
1. ACTIVATION OF AMINO ACID-
• in the cytoplasm present amino acid are in inactive
stage.
• Amino acid activate from giving them energy to joint
them with tRNA.
• Amino acid ia activated by ATP in the presence
specific activing enzymes(E) called amioacyl
synthetases to from aminoacyl adenosine
monophosphate(AA-AMP) and aminoacyl
adenylate(AAA). pyrophasphates(PPi) are released.
• AA+ATP+E AA AMP enzyme
complex.

14. 2.Transfer of amino acid to tRNA
• The activate amino acid is then transfer to specific tRNA.
• Enzyme amino acyl synthetase (E) catalyses the
reaction.
• AMP and activating the enzyme is released during the
process.
AA-AMP-enzyme –complex +tRNA AA-tRNA
+AMP+E
• At the time of transfer,adenylate group (AA) is transfer to
the –OH group of the 3’terminal adenyl nucleotide of a
tRNA.
• There are at least 20 different aminoacyl tRNA
synthetase for binding of 20 different types of amino acid
with 20 different tRNAs.

15. 3.INITIATION OF POLYPEPTIDE
CHAIN
• It requires the ribosomal subunit ,mRNA
an energy source (GTP) aminoacyl
tRNAs(aa-tRNA) and initiation factors (IF)
eIF-1, eIF-2, eIF-3, eIF-4A, eIF-4B, eIF-4D,
eIF-5, eIF-6 in eukaryotes.

16. ELONGATION OF POLYPEPTIDE
CHAIN
• The elongation of polypeptide chain is is brought about
by regular addition of different amino acid with the
respective tRNA at p-site of ribosome.
• The ribosome 2 binding sites for tRNA, an accepter
site (A) and peptidyl site(P).
• Fmet tRNA binds to the p-site of the ribosomes.
• Elongation of polypeptide chain requires elongation
factor(EF).
• Elongation factor EF1 and EF2 is present in
eukaryotes.

17. 17
Ribosomes
• Made of a large and small
subunit
• Composed of rRNA (40) and
proteins (60%)
• Have two sites for tRNA
attachment --- P and A
copyright cmassengale

18. 18
Ribosomes
P
Site
A
Site
Large
subunit
Small
subunit
mRNA
A U G C U A C U U C G
copyright cmassengale

19. 19
Step 1- Initiation
• mRNA transcript start
codon AUG attaches to the
small ribosomal subunit
• Small subunit attaches to
large ribosomal subunit
mRNA transcript
copyright cmassengale

20. Step 2 – Elongation and
translocation
• As ribosome moves, two tRNA with their
amino acids move into site A and P of the
ribosome. this process requires EF,GTP and
Mg++ .
• Peptide bonds join the amino acids.
• The peptide bond formation is catalyzed
byan enzyme peptidyl transferase.
• AA-AA2-tRNA complex when moves from A-
site to P-site ,process called translocation.

21. 21
Initiation
mRNA
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
hydrogen
bonds codon
copyright cmassengale

22. 22
mRNA
A U G C U A C U U C G
1-tRNA 2-tRNA
U A C G
aa1 aa2
A U
A
anticodon
hydrogen
bonds codon
peptide bond
3-tRNA
G A A
aa3
Elongation
copyright cmassengale

23. 23
mRNA
A U G C U A C U U C G
1-tRNA
2-tRNA
U A C
G
aa1
aa2
A U
A
peptide bond
3-tRNA
G A A
aa3
Ribosomes move over one codon
(leaves)
copyright cmassengale

24. 24
mRNA
A U G C U A C U U C G
2-tRNA
G
aa1
aa2
A U
A
peptide bonds
3-tRNA
G A A
aa3
4-tRNA
G C U
aa4
A C U
copyright cmassengale

25. 25
mRNA
G C U A C U U C G
aa1
aa2
A
peptide bonds
3-tRNA
G A A
aa3
4-tRNA
G C U
aa4
A C U
U G A
5-tRNA
aa5
copyright cmassengale

26. 26
mRNA
G C U A C U U C G
aa1
aa2
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
copyright cmassengale

27. TERMINATION
• Termination codon(UAA,UAG,UGA) of mRNA at
3’ end finally reaches at A-site of ribosomes.
• Attachment of releasing factor RF in eukaryotes.
• Hydrolysis of GTP results in the dissociation of
the released factor from the ribosomes. tRNA is
unloaded .the ribosomal unit dissociate and
mRNA is released

28. 28
mRNA
A C A U G U
aa1
aa2
U
primary
structure
of a protein
aa3
200-tRNA
aa4
U A G
aa5
C U
aa200
aa199
terminator
or stop
codon
Termination
copyright cmassengale

29. 29
End Product –The Protein!
• The end products of protein synthesis
is a primary structure of a protein
• A sequence of amino acid bonded
together by peptide bonds
aa1
aa2 aa3 aa4
aa5
aa200
aa199
copyright cmassengale

30. Polysomes
• Each mRNA transcript is read
simultaneously by more than one ribosome.
• A second, third, fourth, etc. ribosome starts
to read the mRNA transcript before the first
ribosome has completed the synthesis of
one polypeptide chain.
• Multiple ribosomes on a single mRNA
transcript are called polyribosomes or
polysomes.
• Multiple ribosomes can not be positioned
closer than 80 nt.

31. POLYSOMES

32. PROCESSING OF RELEASED
POLYPEPTIDE CHAIN
• Released polypeptide chain is a linear molecule
having primary structure.
• It has been seen that the starting amino acid in
polypeptide chain is methionine in eukaryotes.
• Release polypeptide chain is modified in various way:
1. Enzyme deformylase remove formyl 1 group of the 1st
amino acid methionine.
Formyl methionine peptide Formic
acid+methioninyl peptide
2. In presence of specific amino-peptidase enzyme
methionyl peptide is brokeninto methionine and
peptide
methionyl peptide methionine +peptide

33. MAIN DIFFERENCES BETWEEN
PROKARYOTES AND EUKARYOTES
• PROKARYOTES
• Ribosomes-70s
• mRNA –polycistronic
• Initiation codon-N-formil
mithionine
• Initiation factor-IF1, IF2,
IF3.
• Elongation factor-EF-
Tu,EF-Ts,EF-G
• Release factor-
RF1,RF2,RF3
• EUKARYOTES
• Ribosomes-80s
• mRNA- –Monocistronic
• Initiation codon-
mithionine
• Initiation factor-eIF1,e
IF2, eIF3,eIF4A, eIF4B,
eIF4C, eIF4D, eIF5, eIF6.
• Elongation factor-
EF1,EF2
• Release factor-RF.

34. CONCLUSIONS
• Protein is the most important
macromolecles for all living beings that
play most role in the cells.
• Protein synthesized process is known as
translation.
• Many proteins are enzymes that catalyze
biochemical reactions and are vital to
metabolism.

35. REFFERENCES
• CELL BIOLOGY-C.B.POWAR.
• CELL AND MOLECULAR BIOLOGY-
GERALD CARP 4TH ADDITION.
• WWW.NATURE.COM ( 19th
sep12:30PM)
• WWW.SCIENCEDIRECT.COM (18th sep
1:oo PM)
• WWW.ENCYCLOPEDIA.COM. (18th sep
2:30 PM)