TRANSLATION PROCESS IN OUR HUMAN BODY. REGULATION PROTEIN SYNTHESIS IN RIBOSOSMES HAVE DETAILED IN THIS PPT.

1. REGULATION
OF RIBOSOMAL
PROTEIN
SYNTHESIS
MOLECULAR BIOLOGY
BY
KEERTHANA K
II YR B.SC., MICROBIOLOGY

2. ● PROTEIN SYNTHESIS IN
EUKARYOTES
● PROTEIN SYNTHESIS IN
PROKARYOTES
TYPES

3. EUKARYOTES

4. PROTEIN SYNTHESIS IN EUKARYOYES
I. THE RIBOSOMES
II. RIBOSOMAL SITES FOR PROTEIN
TRANSLATION
III.THE PROCESS OF TRANSLATION
IV.INITIATION OF PROTEIN SYNTHESIS
V. ELONGATION OF PROTEIN SYNTHESIS
VI.TERMINATION OF PROTEIN SYNTHESIS

5. ➔Translation involves translating the
sequence mRNA molecule to a
sequence of amino acids
➔Ribosomes in the cytoplasm or ER
synthesize proteins

6. ❖ Ribosomes separate subunits that
composed protein and rRNA.
❖ Eukaryotic ribosomes larger (80S) and
more complex than prokaryotic ribosomes
(70S).
❖ Ribosomes located in cytosol, or
associated ER.
THE RIBOSOMES

7. RIBOSOMAL SITES OF PROTEIN
TRANSLATION
1. THE AMINOACYL-tRNA BINDING SITE
2. THE PEPTIDYL-tRNA BINDING SITE
3. THE EXIT SITE

9. THE PROCESS OFTRANSLATION
★ RIBOSOMAL SEDIMENTATION COEFFICIENT
★ COMPOSITION OF EUKARYOTIC RIBOSOME
★ mRNA-MONOCISTRONIC
★ INITIATION OF PROTEIN SYNTHESIS
★ PROTEIN SYNTHESIS 3 STAGES
1. INITIATION
2. ELONGATION
3. TERMINATION

10. INITIATION
OF PROTEIN
SYNTHESIS
❏ The first step is the formation of a
pre-initiation complex consisting
of the 40S small ribosomal
subunit, Met-tRNAimet, eIF-2 and
GTP.
❏ The pre-initiation complex binds
to the 5’ end of the eukaryotic
mRNA, a step that requires eIF-4F
(also called cap binding complex)
and eIF-3.

12. ❏ The eIF-4F complex consists of eIF-4A,
eIF-4E, and eIF-4G; eIF-4E binds to the 5’
cap on the mRNA whilst eIF-4G interacts
with the poly (A) binding protein on the
poly (A) tail.
❏ The eIF-4A is an ATP-dependent RNA
helicase that unwinds any secondary
structures in the mRNA, preparing it for
translation.
❏ The complex then moves along the
mRNA in a 5’ to 3’ direction until it locates
the AUG initiation codon (i.e. scanning).

13. ELONGATION OF
PROTEIN SYNTHESIS

14. A. Elongation depends eukaryotic elongation factors.
B. 3 elongation factors, eEF-1A, eEF-IB and eEF-2, similar
functions to their prokaryotic counterparts EF-Tu, EF-
Ts and EF-G.
C. At the end initiation step, the mRNA is positioned so
next codon can be translated during the elongation
stage of protein synthesis.
D. The initiator tRNA occupies the P site in the
ribosome, and the A site is ready to receive an
aminoacyl-tRNA.
E. During , each additional amino acid added nascent
polypeptide chain 3-step microcycle.

15. The steps in microcycle are:
➢Positioning the correct aminoacyl-
tRNA in the A site of the ribosome,
➢Forming the peptide bond and
➢Shifting the mRNA by one codon
relative to the ribosome

16. TERMINATION OF PROTEIN SYNTHESIS

17. I. Termination depends on eukaryotic
release factors.
II. Eukaryotic release factor eRF-1
recognizes all three termination codons
(UAA, UAG and UGA) and help protein
eRF-3, terminates translation.
III.Termination, ribosome is disassembled
and completed polypeptide is released.

18. PROKARYOTES

19. PROTEIN SYNTHESIS IN PROKARYOTES
I. THE RIBOSOMES
II. RIBOSOMAL SITES FOR PROTEIN
TRANSLATION
III.THE PROCESS OF TRANSLATION
IV.SYNTHESIS OF AMINOCETYL-tRNA
V. INITIATION OF PROTEIN SYNTHESIS
VI.STEPS INVOLVED
VII.ELONGATION OF PROTEIN SYNTHESIS
VIII.TERMINATION OF PROTEIN SYNTHESIS

20. ➔Translation involves translating
sequence of messenger RNA
(mRNA) molecule to a sequence of
amino acids during protein
synthesis.
➔Process in ribosomes in cytoplasm
or ER synthesize proteins after the
process of transcription of DNA to
RNA.

22. THE RIBOSOMES
❖ Ribosomes separate subunits composed of protein and
rRNA.
❖ The subunits together form ribosome bind to an mRNA,
near its 5’ end.
❖ On binding mRNA, the ribosome reads nucleotide
sequence 5’ to 3’ direction, synthesizing protein from
amino acids in N-terminal (amino-terminal) to C-terminal
(carboxyl terminal) direction.
❖ Ribosomes located cytosol, either floating or associated
with ER.

23. RIBOSOMAL SITES OF
PROTEIN TRANSLATION
1. THE AMINOACYL-tRNA BINDING SITE
2. THE PEPTIDYL-tRNA BINDING SITE
3. THE EXIT SITE

25. THE PROCESS OF TRANSLATION
● Initiation, the mRNA–ribosome complex is
formed and 1st codon binds the first aminoacyl
tRNA (called initiator tRNA).
● Elongation phase, the other codons
sequentially and polypeptide grows addition
of amino acids to its C-terminal end.
● This process continues until a termination
codon (Stop codon), which doesn’t
corresponding aminoacyl-tRNA with which to
base pair.
● Protein synthesis ceases (termination phase)
and the finished polypeptide is released

26. SYNTHESIS OF AMINOACYL-tRNA
Synthesis of aminoacyl-tRNAs is important for two
reasons:
★ Amino acid linked to tRNA molecule, depends
upon the ‘adaptor’ function to ensure that the
correct amino acids are incorporated.
★ The covalent bond formed between amino acid
and tRNA energy bond amino acid to react end
of the growing polypeptide chain form peptide
bond.

27. THE SYNTHESIS OF AMINOACYL tRNA
REFERRED AS AMINO ACID ACTIVATION
1. Cloverleaf secondary structure.
2. The amino acid is covalently
bound
3. Single amino acid.
4. tRNA is catalyzed by an enzyme
called aminoacyl-tRNA
synthetase.

28. SYNTHESIS REACTION
❏ Reaction of an amino acid and ATP to form an aminoacyl-
adenylate (also known as aminoacyl-AMP).
❏ Without leaving the enzyme, the aminoacyl group of
aminoacyl-AMP is transferred to the 3’ end of the tRNA
molecule to form aminoacyl-tRNA.
The overall reaction is:
Amino acid + ATP + tRNA → aminoacyl-tRNA + AMP + PPi

29. INITIATION OF
PROTEIN SYNTHESIS
➢ The first codon translated in mRNAsstart codon or
initiation codon, AUG for methionine.
➢ Two different tRNAs are used two types of AUG
codon; tRNAfMet is used for the initiation codon
and is called the initiator tRNA.
➢ The first amino acid of a new protein is N-
formylmethionine (abbreviated fMet). Hence the
aminoacyl-tRNA used in initiation is fMet-
tRNAfMet.
➢ A short sequence rich in purines (5’-AGGAGGU-3’),
called the Shine–Dalgarno sequence.

30. STEPS INVOLVED
★ Initiation begins with the binding of IF-1 and IF-3 .
★ Their role i stop the 30S subunit binding 50S subunit
absence of mRNA .
★ The small subunit then binds to the mRNA via the Shine–
Dalgarno sequence.
★ The initiator tRNA charged with N-formylmethionine and in
a complex with IF-2 and GTP (fMet-tRNAfMet/IF-2/GTP)
now binds.
★ The complex of mRNA, fMet-tRNAfMet, IF-1, IF-2 and the
30S ribosomal subunit is called the 30S initiation complex.
★ The large (50S) ribosomal subunit now binds, with the
release of IF-1 and IF-2 and hydrolysis of GTP.

31. ELONGATION OF
PROTEIN SYNTHESIS
1. The first round, the initiation codon (AUG) is
positioned in the P site with fMet-tRNAfMet
bound to it via codon–anticodon base pairing.
2. The next codon in the mRNA is positioned in the
A site.

32. ELONGATION 3 STAGES
● AMINOACYL-tRNA BINDING
● PEPTIDE FORMATION
● TRANSLOCATION

33. TERMINATION OF PROTEIN SYNTHESIS
A. Eventually, one of three termination codons (also called
Stop codons). These are UAG, UAA and UGA.
B. Prokaryotic cells do not contain aminoacyl-tRNAs
complementary to stop codons
C. Instead, one of two release factors (RF-1 and RF-2) binds
instead.
D. RF-1 recognizes UAA and UAG whereas RF-2 recognizes
UAA and UGA. A third release factor, RF-3, is also needed
to assist RF-1 or RF-2 interaction with the ribosome.
E. RF-1 (or RF-2) binds at or near the A site whereas RF-
3/GTP binds elsewhere on the ribosome.