2. 1. Template – m RNA
2. Substrates – 20 amino acids.
3. Source of energy – ATP, GTP, energy-
rich bond in amino acyl-tRNAs.
4. Enzymes – specific amino acyl tRNA
synthetases,
peptidyl transferase (ribozyme -28S rRNA
of 60S subunit), protein translation
factors.
5. Product – protein (polypeptide chain).
6. Localization in the cell – cytoplasm
(ribosomes).
3. Activation of amino acids
It requires:
1. 20 amino acids;
2. Enzymes –amino acyl tRNA
synthetases;
3. tRNAs;
4. АTP;
5. Mg²+.
Charging of tRNA
4. Role of tRNA
in protein
biosynthesis:
1. Transport of
amino acid to
the ribosome;
2. Adaptor
function
5. 1. Contains dihydrouracil
residue
2. Acts as the recognition site
for specific aminoacyl tRNA
synthetase
Involved in the
binding of amino acyl
tRNA to ribosomal
surface
6. AMP
AMP tRNA tRNA AMP+
An amino acid An amino acid–AMP
AminoacyltRNA Synthetas
An amino acid–AMP Amino acid–tRNA
ATP Mg2+
8. Translation
Initiation
It requires the following components:
1. mRNA;
2. initiator аа-t-RNA (Met-tRNA);
3. start codon in mRNA (AUG);
4. 40S and 60S subunits;
5. GTP;
6. Eukariotic initiation factors (elF);
7. Mg²+.
9. Formation of 43S pre initiation complex
• 1GTP binds with eIF-2 and forms
binary complex
• Binary complex binds with met
tRNA to form ternary complex
• which binds to 40S subunit of
ribosome to form 43 S complex
10. • Formation of 48S initiation complex
• Binding of 43s complex to mRNA forms
48S complex
Factors are required for this:
- 5’ cap and cap binding complex
(eIF-4 recognizes cap and helps
it to attach 43 S complex)
- eIF-4 controles rate of translation
11. - 43 complex has helicase activity
and unwinds hairpin loops in
mRNA (using ATP)
-It also scan mRNA until not find
AUG codon
-ternary complex binds with AUG
12. • Formation of 80S initiation complex:
(48 S+60 S= 80S)
• Involves GTP hydrolysis:
- eIF5 – hydrolysis of GTP bound
to eIF-2 facilitate 60S association
- Initiation factors are released
14. Translation
Elongation
It requires the following components:
1. initiate complex;
2. complete set of аа-t-РНК;
3. peptidyl transferase;
4. GTP;
5. eukaryotic elongation factors (eEF);
6. Mg²+.
The protein is synthesised from N terminus to its
terminus
15. TRANSLATION
Elongation
Includes 3 steps:
1.binding of an aminoacyl-tRNA to the
A site ;
2.formation of a peptide bond (no ATP
is required);
3. translocation - the whole ribosome
moves one codon along the mRNA.
16. 1.
• Met-tRNA is bound to the P site of ribosome
• mRNA codon in A site determines which
aatRNA will bind to this site
• The incoming aatRNA first combines with
eucariotic elongation factor (eEF) 1,
containing bond with GTP
• When aatRNA-eEF1-GTP complex binds to
A site GTP is hydrolyses to GDP+Pi
• eEF 1 is released
17. 2. Amino acid on the tRNA in the A site
forms
peptide bond with Met on tRNA in the P
site
Peptidyltranferase catalyses formation of
the peptide bond using high energy
bond of aatRNA.
tRNA in A site contains growing
polypeptide chain
18. 3. Translocation involves eEF 2-
GTP complex which binds with
ribosome casing a conformation
cnange and moves ribosome
along mRNA (on one codon)
The uncharged tRNA is released
from ribosome, growing peptidyl-
tRNA moves into P site and next
codon occupies A site of ribosome
26. Many proteins are synthesized in
the inactive form (as (pre)pro-
proteins) and undergo
postsynthetic modification:
– partial proteolysis (removal of
N-terminal Met and the signal
peptide, the formation of active
forms of hormones and enzymes);
– combining the protomers and
the formation of the quaternary
structure of proteins;
27. – the formation of intra- and inter-chain
S-S bonds;
– covalent attachment of cofactors to
the enzymes;
– glycosylation (hormones, receptors,
others);
– the modification of amino acid
residues:
hydroxylation of Pro and Lys
(collagen);
iodination (thyroid hormones);
carboxylation (blood clotting factors);
29. Doxorubicin - it is binding to DNA, generating
free radicals, thereby changing the structure of
DNA in mammalian cells.
Mitomycin С – binds tightly with both strands of
DNA
Inhibitors of replication
30. Inhibitors of trancription
Rifampin inhibits the initiation of transcription by
binding to prokaryotic RNA polymerase.
Rifampin is useful in the treatment of tuberculosis.
Dactinomycin (known to biochemists as actinomycin
D) binds to the DNA template and interferes with the
movement of RNA polymerase along the DNA.
31. ANTIBIOTIC TARGET EFFECT
Erythromycin Prokaryotic 50S
subunit
Blocks translocation
Chloramphenicol Prokaryotic, peptidyl
transferase
Blocks peptide bond
formation
Streptomycin Prokaryotic ribosome Inhibits initiation
Tetracycline Prokaryotic ribosome Blocks binding
aminoacyl tRNA with
A-site
Antibiotics can be used to probe protein synthesis at various stages.
Inhibitors of translation
32. Diphtheria toxin of Corynebacterium diphtheriae catalyzes
the ADP-ribosylation of EF-2 and this modification inactivates
EF-2 in mammalian systems.
Ricin (toxin from the castor bean) inactivates eukaryotic 28S
ribosomal RNA.
Alpha-amanitin ( from Amanita phalloides) inhinits RNA pol
II
Toxins
