The document discusses gene expression, which is the process by which genetic information is used to produce the structures and functions of a cell. It describes the central dogma of molecular biology, in which DNA is transcribed into RNA which is then translated into protein. The key stages of gene expression are explained in detail, including replication, transcription, translation, and post-translational modification. Replication copies DNA, transcription converts DNA into RNA, translation decodes RNA to synthesize protein, and post-translational modifications activate proteins. The document provides a comprehensive overview of the multi-step process of gene expression from DNA to functional proteins.
Transcription in eukaryotes: A brief view
Transcription is the process by which single stranded RNA is synthesized by double stranded DNA. Transcription in eukaryotes and prokaryotes has many similarities while at the same time both showing their individual characteristics due to the differences in organization. RNA Polymerase (RNAP or RNA Pol) is different in prokaryotes and eukaryotes. Coupled transcription is seen in prokaryotes but not in Eukaryotes. In eukaryotes the pre-RNA should be spliced first to be translated.
In Eukaryotic transcription, synthesis of RNA occurs in the 3’→5’ direction. The 3’ end is more reactive due to the hydroxide group. 5’ end containing phosphate groups meanwhile, is not very reactive when it comes to adding new nucleotides. In Eukaryotes, the whole genome is not transcribed at once. Only a part of the genome is transcribed which also acts as the first, principle stage of genetic regulation.
Eukaryotes have five nuclear polymerases:
• RNA Polymerase I: This produces rRNA (23S, 5.8S, and 18S) which are the major components in a ribosome. This also produces pre-rRNA in yeasts.
• RNA Polymerase II: Helps in the production of mRNA (messenger RNA), snRNA (small, nuclear RNA), miRNA. This is the most studied type and requires several transcription factors for its binding
• RNA Polymerase III: This synthesizes tRNA (transfer RNA), 5S rRNA and other small RNAs required in the cytosol and nucleus.
• RNA Polymerase IV: Synthesizes siRNA (small interfering RNA) in plants.
• RNA Polymerase V: This is the least studied polymerase and synthesizes siRNA-directed heterochromatin in plants.
Eukaryotic transcription can be broadly divided into 4 stages:
• Pre-Initiation
• Initiation
• Elongation
• Termination
Transcription is an elaborate process which cells use to copy the genetic information stored in DNA into RNA. This pre-RNA is modified into mRNA before being transcribed to proteins. Transcription is the first step to utilizing the genetic information in a cell. Both Eukaryotes and Prokaryotes employ this process with the basic phases remaining the same. However eukaryotic transcription is more complex indicating the changes transcription has undergone towards perfection during evolution.
An Overview...
Definition of Translation.
Def. of Eukaryotes.
Translation: An Overview.
Components of Translation.
Some Enzymes .
Ribosome Role.
Mechanism of Translation.
Initiation.
Scanning Model of Initiation.
Initiation Factors.
Animation.
Elongation.
Chain Elongation: Translocation.
Animation.
Termination.
Animation....
It's not perfect still... what are your views friends?
This presentation explains DNA transcription and RNA Processing.
It gives details about prokaryotic DNA transcription and eukaryotic DNA transcription. it also explains post-transcriptional modification both in prokaryotes and eukaryotes.
Transcription in eukaryotes: A brief view
Transcription is the process by which single stranded RNA is synthesized by double stranded DNA. Transcription in eukaryotes and prokaryotes has many similarities while at the same time both showing their individual characteristics due to the differences in organization. RNA Polymerase (RNAP or RNA Pol) is different in prokaryotes and eukaryotes. Coupled transcription is seen in prokaryotes but not in Eukaryotes. In eukaryotes the pre-RNA should be spliced first to be translated.
In Eukaryotic transcription, synthesis of RNA occurs in the 3’→5’ direction. The 3’ end is more reactive due to the hydroxide group. 5’ end containing phosphate groups meanwhile, is not very reactive when it comes to adding new nucleotides. In Eukaryotes, the whole genome is not transcribed at once. Only a part of the genome is transcribed which also acts as the first, principle stage of genetic regulation.
Eukaryotes have five nuclear polymerases:
• RNA Polymerase I: This produces rRNA (23S, 5.8S, and 18S) which are the major components in a ribosome. This also produces pre-rRNA in yeasts.
• RNA Polymerase II: Helps in the production of mRNA (messenger RNA), snRNA (small, nuclear RNA), miRNA. This is the most studied type and requires several transcription factors for its binding
• RNA Polymerase III: This synthesizes tRNA (transfer RNA), 5S rRNA and other small RNAs required in the cytosol and nucleus.
• RNA Polymerase IV: Synthesizes siRNA (small interfering RNA) in plants.
• RNA Polymerase V: This is the least studied polymerase and synthesizes siRNA-directed heterochromatin in plants.
Eukaryotic transcription can be broadly divided into 4 stages:
• Pre-Initiation
• Initiation
• Elongation
• Termination
Transcription is an elaborate process which cells use to copy the genetic information stored in DNA into RNA. This pre-RNA is modified into mRNA before being transcribed to proteins. Transcription is the first step to utilizing the genetic information in a cell. Both Eukaryotes and Prokaryotes employ this process with the basic phases remaining the same. However eukaryotic transcription is more complex indicating the changes transcription has undergone towards perfection during evolution.
An Overview...
Definition of Translation.
Def. of Eukaryotes.
Translation: An Overview.
Components of Translation.
Some Enzymes .
Ribosome Role.
Mechanism of Translation.
Initiation.
Scanning Model of Initiation.
Initiation Factors.
Animation.
Elongation.
Chain Elongation: Translocation.
Animation.
Termination.
Animation....
It's not perfect still... what are your views friends?
This presentation explains DNA transcription and RNA Processing.
It gives details about prokaryotic DNA transcription and eukaryotic DNA transcription. it also explains post-transcriptional modification both in prokaryotes and eukaryotes.
Eukaryotic transcription is the elaborate process that eukaryotic cells use to copy genetic information stored in DNA into units of RNA replica.- Source: Wikipedia
INTRODUCTION
HISTORY
WHAT IS TRANSCRIPTION
PROKARYOTIC TRANSCRIPTION
STEPS OF TRANSCRIPTION
HOW TRANSCRIPTION OCCURS
PROCESS OF TRANSCRIPTION
Initiation
Elongation
Termination
CONCLUSION
REFRENCES
Introduction
History
Definition
Classification of DNA Polymerase
Mechanism of DNA Replication
Process of DNA Replication
Initiation
Regulation
Termination
Conclusion
Reference
DNA replication is semi-conservative, one strand serves as the template for the second strand. Furthermore, DNA replication only occurs at a specific step in the cell cycle.
DNA replication in eukaryotes is much more complicated than in prokaryotes, although there are many similar aspects.
DNA replication is a biological process that occurs in all living organisms and copies their DNA; it is the basis for biological inheritance.
Eukaryotic cells can only initiate DNA replication at a specific point in the cell cycle, the beginning of S phase.
Due to the size of chromosomes in eukaryotes, eukaryotic chromosomes contain multiple origins of replication
It is the process of synthesis of protein by encoding information on mRNA.
Protein synthesis requires mRNA, tRNA, aminoacids, ribosome and enzyme aminoacyl tRNA synthase
For MBBS, BDS and General Biochemistry students, coding strand, sense strand, anti-sense strand, promoter, enhancers, silencers, TATA box, Goldberg Hogness box, alternative spilicing, post-transcriptional modification
Eukaryotic transcription is carried out in the nucleus of the cell and proceeds in three sequential stages: initiation, elongation, and termination. Eukaryotes require transcription factors to first bind to the promoter region and then help recruit the appropriate polymerase.
Eukaryotic transcription is the elaborate process that eukaryotic cells use to copy genetic information stored in DNA into units of RNA replica.- Source: Wikipedia
INTRODUCTION
HISTORY
WHAT IS TRANSCRIPTION
PROKARYOTIC TRANSCRIPTION
STEPS OF TRANSCRIPTION
HOW TRANSCRIPTION OCCURS
PROCESS OF TRANSCRIPTION
Initiation
Elongation
Termination
CONCLUSION
REFRENCES
Introduction
History
Definition
Classification of DNA Polymerase
Mechanism of DNA Replication
Process of DNA Replication
Initiation
Regulation
Termination
Conclusion
Reference
DNA replication is semi-conservative, one strand serves as the template for the second strand. Furthermore, DNA replication only occurs at a specific step in the cell cycle.
DNA replication in eukaryotes is much more complicated than in prokaryotes, although there are many similar aspects.
DNA replication is a biological process that occurs in all living organisms and copies their DNA; it is the basis for biological inheritance.
Eukaryotic cells can only initiate DNA replication at a specific point in the cell cycle, the beginning of S phase.
Due to the size of chromosomes in eukaryotes, eukaryotic chromosomes contain multiple origins of replication
It is the process of synthesis of protein by encoding information on mRNA.
Protein synthesis requires mRNA, tRNA, aminoacids, ribosome and enzyme aminoacyl tRNA synthase
For MBBS, BDS and General Biochemistry students, coding strand, sense strand, anti-sense strand, promoter, enhancers, silencers, TATA box, Goldberg Hogness box, alternative spilicing, post-transcriptional modification
Eukaryotic transcription is carried out in the nucleus of the cell and proceeds in three sequential stages: initiation, elongation, and termination. Eukaryotes require transcription factors to first bind to the promoter region and then help recruit the appropriate polymerase.
RNA TRANSCRIPTION AND PROCESSING, DISORDERS OF ABNORMAL POST TRANSLATIONAL MODIFICATION, DRUGS EXPLOITING EUKARYOTIC PROKARYOTIC POST TRANSLATIONAL MODIFICATION
Photosystem II captures and transfers energy.
– chlorophyll absorbs
energy from sunlight
– energized electrons
enter electron
transport chain
– water molecules are
split
– oxygen is released as
waste
– hydrogen ions are
transported across
thylakoid membrane
4.1 Chemical Energy and ATP
• Photosystem I captures energy and produces energycarrying molecules.
– chlorophyll absorbs
energy from sunlight
– energized electrons
are used to make
NADPH
– NADPH is transferred
to light-independent
reactions
4.1 Chemical Energy and ATP
• The light-dependent reactions produce ATP.
– hydrogen ions flow through a channel in the thylakoid
membrane
– ATP synthase attached to the channel makes ATP
4.1 Chemical Energy and ATP
• Light-independent
reactions occur in the
stroma and use CO2
molecules.
The second stage of photosynthesis uses energy from
the first stage to make sugars.
4.1 Chemical Energy and ATP
• A molecule of glucose is formed as it stores some of the
energy captured from sunlight.
– carbon dioxide molecules enter the Calvin Photosystem II captures and transfers energy.
– chlorophyll absorbs
energy from sunlight
– energized electrons
enter electron
transport chain
– water molecules are
split
– oxygen is released as
waste
– hydrogen ions are
transported across
thylakoid membrane
4.1 Chemical Energy and ATP
• Photosystem I captures energy and produces energycarrying molecules.
– chlorophyll absorbs
energy from sunlight
– energized electrons
are used to make
NADPH
– NADPH is transferred
to light-independent
reactions
4.1 Chemical Energy and ATP
• The light-dependent reactions produce ATP.
– hydrogen ions flow through a channel in the thylakoid
membrane
– ATP synthase attached to the channel makes ATP
4.1 Chemical Energy and ATP
• Light-independent
reactions occur in the
stroma and use CO2
molecules.
The second stage of photosynthesis uses energy from
the first stage to make sugars.
4.1 Chemical Energy and ATP
• A molecule of glucose is formed as it stores some of the
energy captured from sunlight.
– carbon dioxide molecules enter the Calvin Photosystem II captures and transfers energy.
– chlorophyll absorbs
energy from sunlight
– energized electrons
enter electron
transport chain
– water molecules are
split
– oxygen is released as
waste
– hydrogen ions are
transported across
thylakoid membrane
4.1 Chemical Energy and ATP
• Photosystem I captures energy and produces energycarrying molecules.
– chlorophyll absorbs
energy from sunlight
– energized electrons
are used to make
NADPH
– NADPH is transferred
to light-independent
reactions
4.1 Chemical Energy and ATP
• The light-dependent reactions produce ATP.
– hydrogen ions flow through a channel in the thylakoid
membrane
– ATP synthase attached to the channel makes ATP
4.1 Chemical Energy and ATP
• Light-independent
reactions occur in the
stroma and use CO2
molecules.
The second stage of photosynthesis uses energy frvf
1.Definition
2.Transcription is selective
3.Transcription in Prokaryotes
•Initiation
•Elongation
•RNA polymerase vs DNA polymerase
•Termination
4.Transcription in Eukaryotes
•Initiation
•Elongation
•Termination
•Post transcriptional modifications
dna transcription is a important topic for biology student. this presentation may be helpful for student of biology.it is useful for all types of courses as like M.Sc, B.Sc, 11th and 12th standard.
Transcription and synthesis of different RNAs
Processing of RNA transcript
Catalytic RNA
RNA splicing and Spliceosome
Transport of RNA through nuclear pore
Translation and polypeptide synthesis
Posttranslational modification
Protein trafficking and degradation
Antibiotics and inhibition of protein synthesis.
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Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
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2. INTRODUCTION
2/7/2016 2
GENE EXPRESSION
It is the process by which a gene's DNA
sequence is converted into the structures and
functions of a cell.
Non-protein coding genes are not translated
into protein.
Genetic information, chemically determined
by DNA structure is transferred to daughter cells
by DNA replication and expressed by
Transcription followed by Translation.
3. 2/7/2016 3
• This series of events is called “Central
Dogma” is found in all cells and proceeds in
similar ways except in retroviruses which
posses an enzyme reverse transcriptase which
converts RNA into complementary DNA.
• Biological information flows from DNA to
RNA , and from there to proteins.
4. 2/7/2016 4
• Gene expression is a multi-step process which
involves
o Replication
o Transcription
o Translation
5. REPLICATION OF DNA
2/7/2016 5
• It is a process in which DNA copies itself to
produce identical daughter molecules of DNA.
• DNA strands are antiparallel and complementary,
each strand can serve as a template for the
reproduction of the opposite strand.
• This process is called semiconservative
replication.
• As the newly synthesized DNA has one half of
the parental DNA and one half of new DNA.
8. INITIATION
2/7/2016 8
DNA replication starts at specific sites called
Origin.
A specific dna A protein binds with this site of
origin and separates the double stranded DNA.
Separation of two strands of DNA results in the
formation of replication bubble with a Replication
Fork on either strands.
A Primer recognises specific sequences of DNA
in the replication bubble and binds to it.
10. 2/7/2016 10
Helicase: The helicase unwinds the DNA helix
by breaking the Hydrogen bonds between the
base pairs.
Topoisomerase: The topoisomerases introduce
negative supercoils and relieve strains in the
double helix at either end of the bubble.
The SSB proteins: The SSB proteins (Single
Strands Binding) stabilize the single strands
thus preventing them to zip back together.
11. ELONGATION
• DNA polymerase III binds to the Template strand
at the 3’ end of the RNA Primer and starts
polymerizing the nucleotides.
• On leading strand polymerization of nucleotides
proceeds in 5’ – 3’ direction towards the replication
fork without interruption.
• Lagging strand is replicated in 5’ – 3’ direction
away from replication fork in pieces known as
Okazaki Fragments.
• As DNA polymerase reaches the 5' end of the RNA
primer of the next Okazaki fragment; it dissociates
2/7/2a016nd re-associates at the 3' end of the primer. 12
12. 2/7/2016 12
• DNA polymerase I remove the RNA primers, and
fills in with DNA.
• DNA ligase seals the nicks and connects the
Okazaki fragments.
• Helicase continues to unwind the DNA into two
ahead of the fork while
relieves the supercoiling caused
single strands
topoisomerases
by this.
13. TERMINATION
2/7/2016 13
• Termination occurs when DNA replication
forks meet one another or run to the end of a
linear DNAmolecule.
• Also, termination may occur when a
replication fork is stopped by a replication
terminator protein.
• DNA Ligase fills up the gaps between the
Okazaki fragments.
• If mistake or damage occurs, enzymes such as
a nuclease will remove the incorrect DNA.
DNA polymerase will then fill in the gap.
14. TRANSCRIPTION
2/7/2016 14
• Transcription is the process through which a
DNA sequence is enzymatically copied by an
RNA polymerase to produce a complementary
RNA or in other words, the transfer of genetic
information from DNA into RNA.
17. 2/7/2016 17
Transcription is divided into 3 stages.
• Initiation
• Elongation
•Termination
INITIATION
• RNA polymerase (RNAP) recognises and
binds to a specific region in the DNAcalled
promoter
18. 2/7/2016 18
• There are two different base sequences on the
coding strand which the RNA polymerase
recognises and for initiation:
• Pribnow box (TATA box) consisting of 6
nucleotide bases (TATAAT) and is located on
the left side about 10 bases upstream from the
starting point of the transcription.
19. 2/7/2016 19
• The ‘-35’ sequence second recognition site in
the promoter region of the DNA and contains a
base sequence TTGACA which is located
about 35 bases upstream of the transcription
starting point.
• Closed complex RNAP
stranded DNA and this
Closed complex.
binds
structure
to double
is called
20. 2/7/2016 20
Open complex After binding of RNAP, the
DNA double helix is partially unwound and
becomes single-stranded in the vicinity of the
initiation site. This structure is called the open
complex.
Elongation
RNA synthesis then proceeds with addition of
ribonucleotide ATP,GTP, CTP and UTP as
building units.
One DNA strand called the template strand
serves as the matrix for the RNA synthesis
21. 2/7/2016 21
• RNAP enzymes transcribe RNA in antiparallel
direction 5’ → 3’. Transcription proceeds in
complementary way :-
Guanine in DNA leads to Cytosine in RNA
Cytosine in DNA leads to Guanine in RNA
Thymidine in DNA leads to Adenine in
RNA
But Thymidine in DNA is replaced by
Uracil in RNA as consequence the
Adenine in DNA shows up for Uracil in
RNA.
22. 2/7/2016 22
• Different types of RNAPs
RNA Polymerase I is located in the nucleolus and
transcribes ribosomal RNA(rRNA).
RNA Polymerase II is localized to the nucleus, and
transcribes messenger RNA (mRNA) and most
small nuclear RNAs (snRNAs).
RNA Polymerase III is localized to the nucleus (and
possibly the nucleolar- nucleoplasm interface), and
transcribes tRNA and other small RNAs
23. 2/7/2016 23
• Termination
• Two termination mechanisms are well known :-
Intrinsic termination (Rho-independent
termination)
Terminator sequences within the RNA that signal the
RNA polymerase to stop. The terminator sequence is
usually a palindromic sequence that forms a stem-loop
hairpin structure that leads to the dissociation of the
RNAP from the DNA template. Example 'GCCGCCG'
The RNA polymerase fails to proceed beyond this
point and the nascent DNA-RNA hybrid dissociates.
24. 2/7/2016 24
Rho-dependent termination uses a
termination factor called ρ factor (rho factor) to stop
RNA synthesis at specific sites.
This protein binds and runs along the mRNA
towards the RNAP. When ρ-factor reaches the RNAP,
it causes RNAP to dissociate from the DNA and
terminates transcription.
25. 2/7/2016 25
• Post transcriptional modification
• Post transcriptional modification is a process in
which precursor messenger RNA is converted into
mature messenger RNA(mRNA).
• The three main modifications are
I. 5' capping
II. 3' polyadenylation
III. RNA splicing
26. 2/7/2016 26
5' capping Addition of the 7 - Methylguanosine cap to
5’ end is the first step in post-mRNA processing. This
step occurs co-transcriptionally after the growing RNA
strand has reached 30 nucleotides.
3' polyadenylation The second step is the cleavage of
the 3' end of the primary transcript following by
addition of a polyadenosine (poly-A) tail.
RNA splicing RNA splicing is the process by which
introns are removed from the mRNA and the remaining
exons connected to form a single continuous molecule.
The splicing reaction is catalyzed by a large protein
complex called the spliceosome.
27. TRANSLATION
2/7/2016 27
It is a process by which proteins are synthesized.
Translation is a complex cellular process where
mRNA molecules, ribosomes, tRNA molecules,
amino acids, aminoacyl synthetases, energy
sources ATP and GTP and a number of factors act
together in a highly coordinated way.
The mRNA carries genetic information encoded
as a ribonucleotide sequence from the
chromosomes to the ribosome.
28. 2/7/2016 28
The ribonucleotides are "read" by translational
machinery in a sequence of nucleotide triplets
called codons. Each of these triplet codes for a
specific amino acid. The ribosome and tRNA
molecules translate this code to produce proteins.
tRNAs have a site for amino acid attachment,
and a site called an anticodon. These anticodon is
an RNA triplet complementary to the codons of
mRNA.
Aminoacyl tRNA synthetase catalyzes the
bonding between specific tRNAs and the amino
acids that their anticodons sequences call for. The
product of this reaction is an aminoacyl-tRNA
molecule.
30. 2/7/2016 30
• Initiation
Initiation of translation is divided into four
stages:-
• Dissociation of Ribosome
Initiation starts with the dissociation of the 80s
ribosome into 40s and 60s subunits.
Initiation factor IF-3 and IF-1A binds to the
40s subunit and prevents its re-associaton with
60s subunit.
31. 2/7/2016 31
• Formation of 43s preinitiation complex
The first aminoacyl tRNA (fmet-tRNA)
binds to the 40s ribosomal subunit and forms
preinitiation complex. Initiation factor IF3 and
IF-1A stabilises this complex.
• Formation of 48s initiation complex
mRNA joins to the 43s preinitiation
complex and forms the 48s initaition complex.
This step requires energy fromATP.
32. 2/7/2016 32
Ribosomal initiation complex scans the
mRNA for the identification of the appropriate
initiation codon and its identification is
facilitated by specific sequence of nucleotide
surrounding it called Kozak Consensus
sequences.
In case of prokaryotes the recognition
sequence of initiation codon is referred to as
Shine-Dalgarno sequence.
33. 2/7/2016 33
• Formation of 80s initiation complex
Initiation ends as the large 60s ribosomal
subunit joins the 48s initiation complex
causing the dissociation of initiation factors.
The binding involves the hydrolysis of GTP.
The step is facilitated by the involvement of
IF-5.
35. 2/7/2016 35
• Elongation
• Elongation of the polypeptide chain involves addition
of amino acids to the carboxyl end of the growing
chain. During elongation the ribosome moves from
the 5’ – end to the 3’ – end of the mRNA that isbeing
translated.
• Elongation is divided into Three steps:-
• Binding of aminoacyl-tRNA to Asite
The 80s initiation complex contains met-tRNAon
the P-site and the A-site is free.
Another aminoacyl-tRNA recognises the codon on
the A-site and binds to it.
This binding is facilitated by elongation factor-1α
and requires energy from GTP.
36. 2/7/2016 36
• Formation of peptide bond
Now the P site contains the beginning of the
peptide chain of the protein to be encoded and
the A site has the next aminoacid to beadded.
The growing polypeptide connected to the
tRNA in the P site is detached from the tRNA
in the P site and a peptide bond is formed
between the last amino acids of the
polypeptide and the amino acid still attached to
the tRNA in the Asite.
38. 2/7/2016 38
• Translocation
Now, the A site has newly formed peptide,
while the P site has an unloaded tRNA (tRNA
with no amino acids).
Then the ribosome moves 3 nucleotides
towards the 3' - end of mRNA.
Since tRNAs are linked to mRNA by codon-
anticodon base-pairing, tRNAs move relative
to the ribosome taking the nascent polypeptide
from the A site to the P site and moving the
uncharged tRNA to the E exit site. This
process is catalyzed by elongation factor EF-2
39. 2/7/2016 39
• Termination
Termination occurs when one of the three
termination codons moves into the Asite.
These codons are recognized by
called release factors, namely
proteins
RF1
(recognizing the UAA and UAG stop codons)
or RF2 (recognizing the UAA and UGA stop
codons).
40. 2/7/2016 40
• These factors trigger the hydrolysis of the ester
bond in peptidyl-tRNA and the release of the
newly synthesized protein from the ribosome.
At the same time the ribosome is dissociate
from the mRNA and recycled and used to
synthesise another protein.
41. 2/7/2016 41
• Protein folding
Protein folding is the process by which a
protein assumes its characteristic functional
shape or tertiary structure, also known as the
native state.
All protein molecules are linear
heteropolymers composed of amino acids; this
sequence is known as the primary structure.
42. Most proteins can carry out their biological
functions only when folding has been
completed, because three-dimensional shape of
the proteins in the native state is critical to
their function.
The process of folding often begins co-
translationally , so that the N-terminus of the
protein begins to fold while the C-terminal
portion of the protein is still being synthesized
by the ribosome.
Specialized proteins called chaperones aid in
2/7/2t01h6 e folding of other proteins. 43
43. 2/7/2016 43
• Posttranslational modification
• Many proteins synthesized by translation are
not functional as such. Many changes takes
place in the protein after synthesis which
converts it into active protein. These are
known as post transcriptional modifications.
44. 2/7/2016 44
• Trimming by Proteolytic Degradation
Many proteins are synthesized as precursors
which are bigger in size than functional
proteins. Some portions
removed by proteolysis
of precursors is
to liberate active
protein . This process is called trimming.
Example formation of insulin from
proinsulin.
45. 2/7/2016 45
• Intein splicing
Inteins are intervening sequences in proteins.
These are comparable to introns in mRNA.
Inteins have to be removed and exteins ligated
in the appropriate order for the protein to
become active.
46. 2/7/2016 46
• Covalent Modifications
Proteins synthesized by translation are
subjected to many covalent changes. By these
changes the proteins are converted to active or
inactive form. The covalent changes include
many modifications such as Phosphorylation,
hydroxylation, Glycosylation, Methylation,
Acetylation etc.