INTRODUCTION HISTORY MECHANISM OF PROTEIN SYNTHESIS TRANSCRIPTION TRANSLATION TRANSCRIPTION INITIATION ELONGATION TERMINATION TRANSLATION AMINOACYLATION OF tRNA INITIATION OF POLYPEPTIDE CHAIN ELONGATION TERMINATION CONCLUSION REFERENCES

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

2. BIOSYNTHESIS OF PROTEIN IN EUKARYOTES
SYNOPSIS:-
 INTRODUCTION
 HISTORY
 MECHANISM OF PROTEIN SYNTHESIS
TRANSCRIPTION
TRANSLATION
 TRANSCRIPTION
INITIATION
ELONGATION
TERMINATION
 TRANSLATION
AMINOACYLATION OF tRNA
INITIATION OF POLYPEPTIDE CHAIN
ELONGATION
TERMINATION
 CONCLUSION
 REFERENCES
SYNOPSIS:-

3. INTRODUCTION:-
Biosynthesis of protein is under direct control of DNA in most cases or else under
control of genetic RNA where DNA is absent.
Information for structure of polypeptide is stored in a polynucleotide chain.
In 1958 Crick proposed that the information present in DNA (in the form of base
sequences) is transferred to RNA and then from RNA it is transferred to protein
(in the form of amino acid sequence)
This relationship between DNA, RNA & Protein molecule is known as Central
dogma.
INTRODUCTION:-

5. •Crick(1958)proposed relationship between DNA,RNA and Protein.
•Nirenberg & Khurana (1968)discovered the complicated DNA code
known as genetic code.
•Albert Clude & George Emil Palade(1974)was awarded the Nobel Prize
for the discovery of the ribosomes.
•Roger D. Kornberg won the 2006 “Nobel Prize in Chemistry”for his
studies of the molecular basis of eukaryotic transcription".
HISTORY:-

6. MECHANISM OF PROTEIN SYNTHESIS:-
Two major steps involved in protein synthesis:-
(1)Transcription:- involving transfer of genetic
information from DNA to RNA , and
(2)Translation:- involving translation of the language
of nucleic acid into that of proteins.

9. MAJOR STEPS OF TRANSCRIPTION :-
There are 3 major steps involved in transcription:
1.INITIATION
2.ELONGATION
3.TERMINATION

10. 1.INITIATION:
Simple diagram of transcription initiation. RNAP = RNA polymerase
The transcription bubble is created by a local unwinding that begins at the site bound
by RNA polymerase.
In eukaryotes, initiation of transcription, requires the presence of a core promoter
sequence in the DNA.
RNA polymerase is able to bind to core promoters in the presence of various specific
transcription factors
The most common type of core promoter in eukaryotes is a short DNA sequence known
as a TATA box , found -30 base pairs from the start site of transcription.
The TATA box, as a core promoter, is the binding site for a transcription factor known as
TATA binding protein (TBP),

11. 2.ELONGATION:
Simple diagram of transcription
elongation
During elongation the enzyme moves along the DNA and extends the growing RNA
chain.
As the enzyme moves, it unwinds the DNA helix to expose a new segment of the
template in single stranded condition.
Behind the unwind region the DNA template strand pairs with its original partner to
reform the double helix.

12. 3.TERMINATION:
It involves the recognition of the point of which no further bases should be
added to the chain.
The sequence of DNA required for those reactions defines the terminator.
The transcription bubble collapses as the DNA-RNA hybrid is disrupted, the
DNA reforms in duplex state and enzyme & RNA are released.
Simple diagram of transcription termination

13. POST TRANSCRIPTIONAL MODIFICATOIN OF mRNA:
The 5’capping
 Poly A tail
 Splicing
 mRNA editing

15. The translation involves the translation of language of nucleic acid
(available in the form of mRNA) into the language of protein.
An mRNA contains a series of codons that interact with the anticodons
of aminoacyl-tRNA so that a corresponding series of amino acid is
incorporated into a polypeptide chain.
Translation proceeds from 5’ to 3’ direction. The direction of growth of
the polypeptide chain starting from the amino-terminal to the carboxy-
terminal residues.
TRANSLATION

16. STAGES NECESSARY COMPONENTS
1.Activation of the amino acids Amino acids
tRNAs
Aminoacyl-tRNA synthases
ATP
Mg++
2.Initiation of polypeptide chain Met-tRNA
Initiation codon in m RNA (AUG)
mRNA
GTP
Mg++
Initiation factors (IF-1,IF-2,IF-3)
40S ribosomal subunit
60S ribosomal subunit
3.Elongation Functional 80S ribosomes
Elongation factors
GTP
4.Termination Functional 80S ribosomes
Termination codon in mRNA
Polypeptide release factors
ESSENTIAL COFACTORS AND SUCESSIVE STAGES IN THE BIOSYNTHESIS OF
PROTEIN

17. COMPONENTS:-
Main components of Translation are;-
1.Ribosome
2.mRNA
3.tRNA
4.Protein factors

18. 1.RIBOSOME:
Ribosomes are made from complexes of RNAs and proteins that are found in the
cytoplasm of both prokaryotes and eukaryotes
Four specific sites on the ribosome are particularly important for protein synthesis
1.mRNA binding site
2. A (aminoacyl) site.
3. P (peptidyl) site
4. E(exit) site

19. 2.tRNA:
Because the amino acid themselves are unable to recognize
different nucleotide codon along the mRNA template, they must
be brought to the correct codon by other molecule, termed as
adapter.
Appropriate to these adaptor, tRNA molecule have two kinds of
specificity;
1.Each tRNA molecule recognizes a specific codon on mRNA .
2.Each carries an amino acid that is specifically chosen to match
that codon according to the dictates of genetic code.

20. Fig. tRNA

21. 3.mRNA:
The heart of mRNA is its message-the sequence of nucleotide that
encode a polypeptide.
The non-translated sequence at the 5’ end of mRNA is called the leader,
because it proceeds the start codon. The start codon is usually AUG; it
can be GUG in eukaryotes.
The non translated sequence at the 3’ end is the trailer, and it follows
the stop codon, which can be UGA,UAG or UAA.

22. 4.PROTEIN FACTORS:
In addition to Aminoacyl-tRNA synthetase,proteins and the protein
constituents of the ribosome, translation also requires the participation
of a number of protein factors.
 Initiation ; eIF1,eIF2,eIF3 etc.
 Elongation ; eEF1,eEF2.
 Termination ; eRF1, eRF2, eRF3

23. THE STEPS OF TRANSLATION:-
The process of translation completed on 4 steps;-
1.AMINOACYLATION OF tRNA
2.Initiation:
•Preparing and checking the mRNA
•Binding the initiator tRNA
•mRNA binding and scanning
•Association of the large subunit
3.Elongation:
•Binding of new aminoacyl t-RNA at the A site
•Formation of new peptide bond
•Translocation of ribosome
4.Termination:
•Binding of release factors
•Hydrolysis of the peptidyl t-RNA

24. 1. AMINOACYLATION OF tRNA
It occurs in two steps:-
1) Amino acid + ATP Aminoacyl-AMP + iP
2) Aminoacyl-AMP + tRNA Aminoacyl-tRNA +
AMP
Both the reactions are catalyzed by same enzyme i.e.
Aminoacyl-tRNA synthetase.

25. 2.INITIATION:-
The initiation phase of protein synthesis requires over 10 eukaryotic
Initiation Factors (eIFs)
eIF1
eIF1A
eIF2
eIF3
eIF4A
eIF4E
eIF4F
eIF4G
eIF5
eIF5B
We can view initiation in following stages:

26. Preparing and checking of mRNA

27. Formation of
ternary complex
Ribosomal
dissociation
Formation of 43s
preinitiation
complex
Formation of 48s
initiation complex
Formation 80s
initiation complex
Fig. Initiation of translation

29. 3.ELONGATION:-
Every amino acid addition to a growing polypeptide chain is the result of an
elongation cycle.
Three special Elongation Factors are required for this phase of protein
synthesis: eEF-1a (GTP), eEF-1bg and EF-G (GTP).
3 stages involved in elongation process;
 Binding of a new aminoacyl-tRNA at the A site
 Formation of the new peptide bond (Transpeptidation)
 Translocation of the Ribosome

30. Fig. process of Elongation
Binding of a new
aminoacyl-tRNA at the
A site
Formation of the new
peptide bond
(Transpeptidation)
Translocation of the
Ribosome

31. 4.TERMINATION:-
Protein synthesis stops when ribosome reaches one of three special nonsense
codons- UAA, UGA, UAG.
Three release factors ( eRF1, eRF2, eRF3-GTP ) add the ribosome in
recognizing these codons.
eRF1 recognizes the UAA &UGA stop codons
eRF2 recognizes the UAA &UAG stop codons
eRF3(GTP) stimulates the binding of RF1 & RF2
These process is completed on two steps;
 Binding of Release factors
 Hydrolysis of the peptidyl-tRNA

32. Fig. Process of Termination
 Binding of Release
factors
 Hydrolysis of the
peptidyl-tRNA

33. Fig. Translation Process

34. CONCLUSION:-

35. S.No BOOKS AUTHOR
1. Biochemistry(2008) Lehninger
2. Gene IX (2008) Benjamin Lewin
3. The world of cell Becker et al
4. Biochemistry Stryer
5. Microbiology(1997) Tortora, Funke,Case
6. Internet www.google.com
REFERENCES:-