Protein targeting or protein sorting is the mechanism by which a cell transports to the appropriate positions in the cell or outside of it. Both in prokaryotes and eukaryotes, newly synthesized proteins must be delivered to a specific sub-cellular location or exported from the cell for correct activity. This phenomenon is called protein targeting. Protein targeting is necessary for proteins that are destined to work outside the cytoplasm.This delivery process is carried out based on information contained in the protein itself. Correct sorting is crucial for the cell; errors can lead to diseases. In 1970, Günter Blobel conducted experiments on the translocation of proteins across membranes. He was awarded the 1999 Nobel Prize for his findings. He discovered that many proteins have a signal sequence, that is, a short amino acid sequence at one end that functions like a postal code for the target organelle.
The delivery of newly synthesized protein to their proper cellular destination, usually referred to as protein targeting or sorting.
The mode of protein transport depends chiefly on the location in the cell cytoplasm of the polysomes involved in protein synthesis.
There are two modes of protein sorting:-
1) Co - translational Transportation.
2) Post - translational Transportation.
Folding depends upon sequence of Amino Acids not the Composition. Folding starts with the secondary structure and ends at quaternary structure.
Denaturation occur at secondary, tertiary & quaternary level but not at primary level.
Protein targeting or protein sorting is the biological mechanism by which proteins are transported to their appropriate destinations in the cell or outside it. Proteins can be targeted to the inner space of an organelle, different intracellular membranes, plasma membrane, or to exterior of the cell via secretion.
Protein targeting or protein sorting is the mechanism by which a cell transports to the appropriate positions in the cell or outside of it. Both in prokaryotes and eukaryotes, newly synthesized proteins must be delivered to a specific sub-cellular location or exported from the cell for correct activity. This phenomenon is called protein targeting. Protein targeting is necessary for proteins that are destined to work outside the cytoplasm.This delivery process is carried out based on information contained in the protein itself. Correct sorting is crucial for the cell; errors can lead to diseases. In 1970, Günter Blobel conducted experiments on the translocation of proteins across membranes. He was awarded the 1999 Nobel Prize for his findings. He discovered that many proteins have a signal sequence, that is, a short amino acid sequence at one end that functions like a postal code for the target organelle.
The delivery of newly synthesized protein to their proper cellular destination, usually referred to as protein targeting or sorting.
The mode of protein transport depends chiefly on the location in the cell cytoplasm of the polysomes involved in protein synthesis.
There are two modes of protein sorting:-
1) Co - translational Transportation.
2) Post - translational Transportation.
Folding depends upon sequence of Amino Acids not the Composition. Folding starts with the secondary structure and ends at quaternary structure.
Denaturation occur at secondary, tertiary & quaternary level but not at primary level.
Protein targeting or protein sorting is the biological mechanism by which proteins are transported to their appropriate destinations in the cell or outside it. Proteins can be targeted to the inner space of an organelle, different intracellular membranes, plasma membrane, or to exterior of the cell via secretion.
Proteins destined for secretion, integration in the plasma membrane, or inclusion in lysosomes generally share pathway that begins in the endoplasmic reticulum. Proteins destined for mitochondria, chloroplasts, or the nucleus use three separate mechanisms. And proteins destined for the cytosol simply remain where they are synthesized.
Proteins destined for secretion, integration in the plasma membrane, or inclusion in lysosomes generally share pathway that begins in the endoplasmic reticulum. Proteins destined for mitochondria, chloroplasts, or the nucleus use three separate mechanisms. And proteins destined for the cytosol simply remain where they are synthesized.
How are proteins imported into the thylakoids of chloroplastsSo.pdffootwearpark
How are proteins imported into the thylakoids of chloroplasts?
Solution
Answer:
Nuclear-encoded thylakoid proteins are first imported into the chloroplast and then directed to
the thylakoid using different sorting mechanisms.
The proteins targeted for chloroplasts contain transit peptide sequence called stromal import
sequence or a stromal and thylakoid targeting sequence.
Import receptors and translocation complexes aid in targeting the protein to its respective
location. The endoproteases in stroma remove transit peptide sequences and the proteins fold into
functional form.
Proteins of the outer membrane complex are called Tocs
Inner membrane translocon complex proteins are called Tics
Proteins destined for thylakoid membrane will have both stromal and thylakoid targeting
sequence. cpSRP pathway is used for the insertion of these integral membrane proteins into the
thylakoid membrane..
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
3. THE CENTRAL DOGMA
•DNA synthesis maintains the genetic
information and passes this to the next
generation
•RNA synthesis (transcription) is a
transfer of the information from the DNA
where it is stored into RNA which can be
transported and interpreted.
•Ribosomes translate the nucleotides on
the mRNA into amino acid sequences
producing a polypeptide
5. TRANSLATION
● Initiation – the assembly of a
ribosome on an mRNA molecule.
● Elongation – repeated cycles
of amino acid addition.
● Termination – the release of
the new protein chain.
6. PROTEIN TARGETING
Both in prokaryotes and eukaryotes, newly synthesized
proteins must be delivered to a specific subcellular location or
exported from the cell for correct activity. This phenomenon is
called protein targeting.
• Protein targeting is necessary for proteins that are destined
to work
outside the cytoplasm.
• This delivery process is carried out based on information
contained in the protein itself.
• Correct sorting is crucial for the cell; errors can lead to
diseases.
7. PROTEIN TRANSLOCATION
In 1970, Günter Blobel conducted experiments on
the translocation of proteins across membranes.
He was awarded the 1999 Nobel Prize for his
findings. He discovered that many proteins have a
signal sequence, that is, a short amino acid
sequence at one end that functions like a postal
code for the target organelle.
9. POSTTRANSLATIONAL TRANSLOCATION
Even though most proteins are co translationally
translocated, some are translated in the cytosol
and later transported to their destination. This
occurs for proteins that go to a mitochondrion, a
chloroplast, or a peroxisome
10. CO TRANSLATIONAL TRANSLOCATION
Synthisised protein is transferred to an SRP receptor on
the endoplasmic reticulum (ER), a membrane-
enclosed organelle. There, the nascent protein is
inserted into the translocation complex
11. TARGETING SIGNALS
Targeting signals are the pieces of information that enable the cellular
transport machinery to correctly position a protein inside or outside the
cell.
This information is contained in the polypeptide chain or in the folded
protein.
In the absence of targeting signals, a protein will remain in the
cytoplasm
The continuous stretch of amino acid residues in the chain that enables
targeting are called signal peptides or targeting peptides.
There are two types of targeting peptides.
The presequences and
The internal targeting peptides
12. THE PRESEQUENCES
The presequences of the targeting peptides are
often found at the N-terminal extension .
It is composed of between 6-136 basic and
hydrophobic amino acids.
In case of peroxisomes the targeting sequence is
on the C-terminal extension mostly.
signal sequences are removed from the finished
protein by specialized signal peptidases once the
sorting process has been completed
13. THE INTERNAL TARGETING PEPTIDES
the targeting peptides are often found at the with in
polypeptide chain, not at any end .
14.
15. PROTEINS CAN MOVE BETWEEN
COMPARTMENTS IN DIFFERENT WAYS
Gated transport(Nucleus )
Transmembrane
transport(Mitochondria,
Peroxisomes,)
Vesicular transport (E.R)
16. GATED TRANSPORT
The protein traffic
between the cytosol and
nucleus occurs between
topologically equivalent
spaces, which are in
continuity through the
nuclear pore
complexes.
The nuclear pore
complexes function as
selective gates that
actively transport
specific
macromolecules and
macromolecular
assemblies,
17. TRANSMEMBRANE TRANSPORT
Membrane-bound protein
translocators directly transport
specific proteins across a
membrane from the cytosol into
a space that is topologically
distinct.
The transported protein molecule
usually must unfold to snake
through the translocator.
The initial transport of selected
proteins from the cytosol into the
ER lumen or from the cytosol
into mitochondria.
18. VESICULAR TRANSPORT
Proteins from the ER to the Golgi
apparatus and proteins to E.R,
for example, occurs in this way.
transport intermediates— which
may be small, spherical transport
vesicles or larger, irregularly
shaped organelle fragments—
ferry proteins from one
compartment to another.
The transfer of soluble recognized
by a complementary receptor in
the appropriate membrane.
20. THE TRANSPORT OF MOLECULES BETWEEN THE
NUCLEUS AND THE CYTOSOL
The nuclear envelope encloses the DNA and defines the nuclear
compartment.
This envelope consists of two concentric membranes that are
penetrated by nuclear pore complexes.
The inner and outer nuclear membranes are continuous, they maintain
distinct protein compositions.
The inner nuclear membrane contains specific proteins that act as
binding sites for chromatin and for the protein meshwork of the nuclear
lamina that provides structural support for this membrane.
The inner membrane is surrounded by the outer nuclear membrane,
which is continuous with the membrane of the ER. Like the membrane of
the ER the outer nuclear membrane is studded with ribosomes engaged
in protein synthesis .
The proteins made on these ribosomes are transported into the
space between the inner and outer nuclear membranes (the
perinuclear space), which is continuous with the ER lumen. with
ribosomes engaged in protein synthesis.
Bidirectional traffic occurs continuously between the cytosol and the
nucleus.
The many proteins , histones, DNA and RNA polymerases, gene
regulatoryimported into the nuclear compartment from the cytosol,
proteins, and RNA-processing proteins are selectively tRNAs and
mRNAs are synthesized in the nuclear compartment and then exported to
the cytosol
21. IMPORT AND EXPORT OF PROTEINS
TO NUCLEUS Protein encodes a receptor
protein that is specialized for the
transport of a group of nuclear
proteins sharing structurally
similar nuclear localization
signals.
Nuclear import receptors do not
always bind to nuclear proteins
directly. Additional adaptor
proteins are sometimes used that
bridge between the import
receptors and the nuclear
localization signals on the
proteins to be transported.
Export -ribosomal subunits and
RNA molecules.
For import and export requires
energy
23. MITOCHONDRIA AND CHLOROPLASTS
Mitochondria and chloroplasts are double-
membrane-enclosed organelles.
They specialize in the synthesis of ATP, using
energy derived from electron transport and
oxidative phosphorylation in mitochondria and
from photosynthesis in chloroplasts.
Both organelles contain their own DNA,
ribosomes , and other components required for
protein synthesis .
Their growth depends mainly on the import of
proteins from the cytosol.
25. •Protein translocation across
mitochondrial membranes is
mediated by multi-subunit protein
complexes that function as protein
translocators.
•TOM ,TIM 23,TIM22 ,OXA
•TOM transports-mitochondrial
precursor proteins , nucleus-
encoded mitochondrial proteins.
•TIM23-proteins into the matrix
space.
•TIM22-mediates the insertion of
a subclass of inner membrane
proteins, including the carrier
protein that transports ADP, ATP,
and phosphate.
•OXA-mediates the insertion of
inner membrane proteins .
26. PROTEIN TRANSPORT INTO THE MITOCHONDRIA
Import of Mitochondrial Proteins
►Post-translational: Unfolded polypeptide chain
1. precursor proteins bind to receptor proteins of TOM
2. interacting proteins removed and unfolded polypetide is fed into
translocation channel
►Occurs contact sites joining IM and OM - TOM transports mito targeting signal across
OM and once it reaches IM targeting signal binds to TIM, opening channel complex thru
which protein enters matrix or inserts into IM
27. PROTEIN TRANSPORT INTO THE MITOCHONDRIA
Import of Mitochondrial Proteins
►Requires energy in form of ATP and H+ gradient and assitance of hsp70
-release of unfolded proteins from hsp70 requires ATP hydrolysis
-once thru TOM and bound to TIM, translocation thru TIM requires
electrochemical gradient
28. PROTEIN TRANSPORT INTO THE MITOCHONDRIA
Protein Transport into IM or IM Space Requires 2 Signal Sequences
1. Second signal =hydrophobic sequence; immediately after 1st signal sequence
2. Cleavage of N-terminal sequence unmasks 2nd signal used to translocate protein from
matrix into or across IM using OXA
3. OXA also used to transport proteins encoded in mito into IM
4. Alternative route bypasses matrix; hydrophobic signal sequence = “stop transfer”
29. CHLOROPLAST
The preprotein for chloroplasts
may contain a stromal import
sequence or a stromal and
thylakoid targeting sequence.
The majority of preproteins are
translocated through the Toc
and Tic complexes located
within the chloroplast envelope.
In the stroma the stromal
import sequence is cleaved off
and folding as well as intra-
chloroplast sorting to thylakoids
continues.
Proteins targeted to the
envelope of chloroplasts
usually lack cleavable sorting
sequence.
30. TRANSLOCATION OF PROTEIN IN
CHLOROPLAST
The vast majority of chloroplast proteins are
synthesized as precursor proteins (preproteins)
in the cytosol and are imported post-
translationally into the organelle.
Most proteins that are destined for the
thylakoid membrane,
Preproteins that contain a cleavable transit
peptide are recognized in a GTP-regulated
manner12 by receptorsof the outer-envelope
translocon, which is called theTOC complex.
The preproteins cross the outer envelope
through an aqueous pore and are then
transferred to the translocon in the inner
envelope,which is called the TIC complex.
The TOC and TIC translocons function
together during the translocation process
Completion of import requires energy,which
probably comes from the ATP-dependent
functioning of molecular chaperones in the
stroma.
The stromal processing peptidase then
cleaves the transit sequence to produce the
mature form of the protein, which can fold into
its native form.
31. THE ENDOPLASMIC RETICULUM
All eukaryotic cells have an endoplasmic reticulum (ER). Its membrane
typically constitutes more than half of the total membrane of an average
animal cell.
The ER is organized into a netlike labyrinth of branching tubules and
flattened sacs extending throughout the cytosol , to interconnect.
The ER has a central role in lipid and protein biosynthesis.
Its membrane is the site of production of all the transmembrane proteins
and lipids for most of the cell’s organelles( the ER itself, the Golgi apparatus,
lysosomes, endosomes, secretory vesicles, and the plasma membrane).
The ER membrane makes a major contribution to mitochondrial and
peroxisomal membranes by producing most of their lipids.
almost all of the proteins that will be secreted to the cell exterior plus those
destined for the lumen of the ER, Golgi apparatus, or lysosomes are initially
delivered to the ER lumen.
37. Those ER resident proteins that
escape from the ER are
returned to the ER by vesicular
transport.
(A) The KDEL receptor present
in vesicular tubular clusters and
the Golgi apparatus, captures
the soluble ER resident proteins
and carries them in COPI-
coated transport vesicles
back to the ER. Upon binding its
ligands in this low-pH
environment, the KDEL receptor
may change conformation, so
as to facilitate its recruitment
into budding COPI-coated
vesicles.
(B) The retrieval of ER proteins
begins in vesicular tubular
clusters and continues from all
parts of the Golgi apparatus.
39. THE GOLGI APPARATUS
The Golgi apparatus is integral in
modifying, sorting, and packaging
these macromolecules for cell
secretion (exocytosis) or use within
the cell.
Post office; it packages and labels
items(a mannose-6-phosphate label
to proteins destined for lysosomes)
which it then sends to different parts
of the cell.
glycosylation refers to the enzymatic
process that
attaches glycans to proteins, lipids, or
other organic molecules.
Glycosylation is a form of co-
translational and post-translational
modification
40. Five classes of glycans are produced:
N-linked glycans attached to nitrogen of asparagine or arginine side-
chains. N-linked glycosylation requires participation of a special lipid
called dolichol phosphate.
O-linked glycans attached to the hydroxy oxygen of serine,
threonine, tyrosine, hydroxylysine, or hydroxyproline side-chains, or
to oxygens on lipids such as ceramide
phospho-glycans linked through the phosphate of a phospho-serine;
C-linked glycans, a rare form of glycosylation where a sugar is added
to a carbon on a tryptophan side-chain
Glypiation, which is the addition of a GPI anchor that links proteins to
lipids through glycan linkages.
42. SUMMARY
Both in prokaryotes and eukaryotes, newly synthesized
proteins must be delivered to a specific subcellular
location or exported from the cell for correct activity. This
phenomenon is called protein targeting. Secretory
proteins have an N-terminal signal peptide which targets
the protein to be synthesized on the rough endoplasmic
reticulum (RER). During synthesis it is translocated
through the RER membrane into the lumen. Vesicles
then bud off from the RER and carry the protein to the
Golgi complex, where it becomes glycosylated. Other
vesicles then carry it to the plasma membrane. Fusion
of these transport vesicles with the plasma membrane
then releases the protein to the cell exterior.
43. REFERENCES
Biochemistry, Third Edition ( David Hames & Nigel
Hooper, )
Molecular Biology, Third Edition ( Phil Turner, Alexander
McLennan,Andy Bates & Mike White)
Palade G (1975) Intracellular aspects of the process of
protein synthesis.Science 189, 347–358.
Lodish, H., Berk, A., Zipursky, S.L., Matsudaira, P.,
Baltimore, D., Darnell, J., 2000, Molecular Cell Biology,
4th Ed., W.H. Freeman.
http://bcs.whfreeman.com/lodish5e/
Lehninger principles of Biochemistry, Fourth edition ,
David L. Nelson, Michael M. Co