Translation in prokaryotes Central dogma, ribosomes, initiation, elongation, termination.

1. PG DEPARTMENT OF BIOTECHNOLOGY
SAHYADRI SCIENCE COLLEGE, SHIVAMOGGA-577203
A SEMINAR REPORT ON
“TRANSLATION IN PROKAYOTES”
UNDER THE GUIDENCE OF
Dr . Prabhakar BT
Associate Professor
PG Department of
Biotechnology
Sahyadri Science College
Shivamogga-577203
SUBMITTED BY
M.JYOTHIKA
1‫׀‬MSc ‫׀‬ 1SEM
PG Department of Biotechnology
Sahyadri Science College
Shivamogga-577203

2. CONTENTS
INTRODUCTION
CENTRAL DOGMA
PROTEIN SYNTHESIS
INITIATION
ELONGATION
TERMINATION
 OVERVIEW OF TRANSLATION

3. INTRODUCTION
 It is the process of synthesis of protein from messenger RNA transcripts (mRNA) after the process of
transcription of DNA to RNA
 It place in the cytoplasm by specialised organelle known as ribosome.
 There are no endoplasmic reticulum in the prokaryotes and ribosomes are suspended in the cytoplasm,
whereas endoplasmic reticulum are present in eukaryotes which harbors ribosomes-translation takes place
on rough endoplasmic reticulum (RER) in eukaryotes, whereas translation occurs freely in cytoplasm in the
prokaryotes.
 The codons on the mRNA are translated into amino acid sequence which leads to the synthesis as protein.
 Translation requires a variety of cellular components, such as proteins, RNAs and different small
molecules.
 It has also three main steps:
 Initiation- Formation of mRNA-ribosome complex
 Elongation- Formation of polypeptide chain complimentary to the mRNA
 Termination- Termination of polypeptide chain.

4. CENTRAL DOGMA
 Flow of genetic information on a cell
-How do we move information from DNA to
proteins?
 “It states that genetic information is transmitted from
DNA to RNA to Protein and this information cannot be
transferred back from protein to either protein or nucleic
acid”.

5. WOBBLE HYPOTHESIS
 There are more than one codon for one amino acid. This is
called degeneracy of genetic code.
 To explain the possible cause of degeneracy of codons, in
1966, Francis Crick proposed “the wobble hypothesis”.
 According to this hypothesis, only the first two bases of
the codon have a precise pairing with bases of the
anticodon of tRNA, while the pairing between the third
bases of codon and anticodon may wobble(wobble means
to sway or move unsteadily).
 The phenomenon permits a single tRNA to recognize more
than one codon. therefore, although there are61 codons for
amino acids, the number of tRNA is far less(around40)
which is due to wobbling.

6. RIBOSOMES
 It is made up of rRNA and proteins.
 70s ribosome occur in prokaryotic cells.
 It consists of two subunit smaller(30s) and
larger(50s).
 Larger subunit consists of three site: A site, P
site, E site.

7. 30S RIBOSOMAL SUBUNIT
 30s subunit, is the smaller subunit of the 70s
ribosome found in prokaryotes.
 It is the complex of the 16s ribosomal RNA
(rRNA) and 19 proteins.

8. 50S RIBOSOMAL SUBUNIT
 50s is the larger subunit of the 70s ribosome of
prokaryotes, i.e. bacteria and archaea.

9. TRANSFER RNA
 It contains three structural loops joined by
hydrogen bonding.
 Transfer RNA brings or transfers amino acids to
the ribosomes.

10. VARIOUS PROTEINSFACTORS INVOLVEDIN PROTEINSYNTHESIS
FACTORS
IF-1
IF-2
IF-3
EF-TU
EF-TS
EF-G
RF-1
TRANSLATION STEPS
INITIATION
INITIATION
INITIATION
ELONGATION
ELONGATION
ELONGATION
TERMINATION
FUNCTIONS
Helps to stabilize 30s ribosomal
subunit
Binds Fmet -tRNA withs30s
subunit mRNA complex; bind GTP
and hydrolyse.
Binds 30s subunit with mRNA
Binds GTP; bring Aminoacyl-tRNA
to A site of ribosome
Generates EF-TU
Helps in translocation of ribosome
Helps to dissociates polypeptide
from tRNA ribosome complex;
specific for UAA and UGA

11. RF-2
RF-3
TERMINATION
TERMINATION
Helps to dissociates polypeptide;
specific for UGA and UAA
Stimulates RF-1 and RF-2

12. PROTEIN SYNTHESIS
Three steps ;
 Initiation: It brings together mRNA, ribosomal subunits and initiator
tRNA.
 Elongation: In this phase, adding of amino acids take place based on
codon sequence.
 Termination: Here codon ends and translation stops

13. ACTIVATIONOF AMINO ACID
 The activation of amino acids take place in cytosol.
 The activation of amino acids is catalysed by their aminoacyl
tRNA synthetases.
 All the 20 amino acids are activated and bound to 3’ end of
their specific tRNA in the presence of ATP and Mg++.

14. 1.INITIATION TRANSLATION
 Initiation of translation in
prokaryotes involves the
assembly of the components of
the translation system which
are:
 The two ribosomal subunits
(small and large)
 The mRNA to be translated,

15. 2.ELONGATION TRANSLATION
 Elongation begins after the
formation of the initiation complex.
 Elongation means length of
polypeptide chain in increasing.
 This process complete in three steps
 Binding of aminoacyl tRNA to A site
 Peptide bond formation
 Ribosomal Translocation
 There are three elongation factor
involve:
 EF-Tu, EF-Ts, EF-G

16. BINDING OF AMINO ACYL TRNA TO A SITE
 The 2nd tRNA carrying next amnio acid comes into A site
and recoginse the codon mRNA. This binding is
facilitated by EF-Tu-GDP.

17. PEPTIDE BOND FORMATION
 The amino acid present in tRNA of
P-site, Fmet is transferred to tRNA
of A-site forming peptide bond. This
reaction is catalysed by peptidyl
transferase
 Now, the tRNA at P-site become
uncharged

18. RIBOSOME TRANSLOCATION
• After peptide bond formation ribosome moves one
codon ahead along 5’-3’ direction on mRNA, so that
dipeptide-tRNA appear on P-site and next codon
appear on A-site.
• The uncharged tRNA exit from ribosome and enter
to cytosol.

19. 3.TERMINATIONOF TRANSLATION
 This is last phase of translation.
 Termination occurs when one of the three
termination codons moves into the A-site.
 These codons are not recognized by proteins
called release factors, namely RF1
 Step 1 – After the amino acids needed to make
the protein required are properly bonded to
each other a release factors binds to the
complex when a stop codon enters the A site.
 Step 2 – The release factor then disconnects the
polypeptide from the tRNA in the P site.
 Step 3 – The remaining components mRNA,
ribosomal subunit, and the protein are released
and the process of translation ends

20. OVERVIEWOF TRANSLATION

21. CONCLUSION
Prokaryotic translation is a highly regulated and intricate
process essential for protein synthesis with in these simple
cells. Translational initiation, elongation, and termination are
coordinated through the interaction of ribosomal RNA and
proteins, with messenger RNA providing the template for
protein assembly. The involvement of initiation factors,
elongation factors, and release factors, alongside other
factors, ensures the precision and efficiency of this process.
However, despite its complexity, prokaryotic translation
remains a vital component of cellular function and is a target
for regulation in response to various environmental cues.

22. REFERENCES
 Willey J., Sherwood L., Woolverton C.J. 2017. Prescott’s Microbiology
10th Edition, McGraw Hill publication, New York, USA
 Kerbs J.E., Goldstein E.S,. Kilpatrick S.T. 2017. Lewis Genes X11. jones
and Bartlett publishers, Inc., Burlington, MA, USA