Molecular chaperones

1. Molecular
Chaperones
Present by
Rizwan abbas
M Anas
M junaid

2. Molecular Chaperones
• Out line
• Introduction
• Properties
• Mechanism of Action
• Types
• Example
• Benefits

3. Introduction
Definition
• Chaperones can be defined as
proteins
• which monitor non-native
conformations, stabilize
proteins and assist folding
processes,
• but are not part of the final
native structures .They
optimize the folding efficiency
or even facilitate folding
Another definitions
• Chaperonins are proteins Protein
folding is assisted by a group of
proteins known as molecular
chaperones
• that provide favorable
conditions for the correct folding
of other proteins,
• thus preventing aggregation.
Newly made proteins usually
must fold from a linear chain of
amino acids into a three-
dimensional form.

4. Another definitions
Ellis, 1993:
• Molecular chaperones are
defined as a functional class of
unrelated families of proteins
• that assist the correct non-
covalent assembly of other
polypeptide containing
structures in vivo, but are not
components of these
assembled structures when
they are performing their
normal biological functions.”
Anfinsen in 1973 said
• “Molecular chaperones are
the guardians of protein
homeostasis. Proteins
require a particular three
dimensional structure in
order to fulfil their function,
despite being synthesised as
a linear string of amino
acids joined by peptide
bonds.”

5. According Mayer view
2010
• Molecular chaperones are catalysts in the physiological
folding process,
• which, through transient non-covalent associations with
proteins, prevent aggregation and misfolding
• during de novo folding as well as regulating subsequent
stages of protein translocation and complex formation.

6. Where are the molecular
chaperones located?
• Molecular chaperones are found in all compartments of a cell where folding or,
more generally, conformational rearrangements of proteins occur.
• • It is not necessarily that all molecular chaperone families are present in
the three domains of life; some are highly specialized and are found in just one
domain
• • Eukaryotes have evolved not only more different families of chaperones,
but typically have more members (e.g., Hsp70, small Hsps, prefoldin, etc.)
• • related to diversity of processes? (eukaryotes have organelles, greater
diversity of cell functions)
• • In bacteria, the archetype is the well-characterized chaperonin GroEL
from E. coli.
• • In archaea, the chaperonin is called the thermosome.
• • In eukarya, the chaperonin is called CCT (also called TRiC or c-cpn).

7. Structure of Chaperone

8. properties
• Protein in nature
• Specific
• Active
• Use ATP energy
• Found in ER and cytosol
• •A typical feature of chaperones is the stoichiometric and transient binding
of non-native polypeptides mostly at exposed hydrophobic patches.
• •Chaperone binding stabilizes productive folding intermediates, hinders
non-native proteins from building incorrect intra- and intermolecular
interactions and in this way reduces protein misfolding and aggregation.
• • In some instances, chaperone binding additionally triggers transient
local unfolding and Chaperones may act as “holdases” stabilizing non-native
protein conformations, as “foldases” assisting folding to the native state or as
“unfoldases” unfolding misfolded protein species or extracting proteins from
aggregatesand .

9. Types
• On the basis of the functioning mode in specific points
molecular chaperones are categorized as follows
• Intra molecular chaperones

10. Intra molecular
chaperones
• Intra molecular chaperones are essential for protein
folding, but not required for protein function.
• Considerable evidence shows that chaperones play a
critical role in protein folding both in vivo and in vitro.
• Unlike their molecular counterparts, intra molecular
chaperones are encoded in the primary sequence of the
protein as an N-terminal or C-terminal sequence
extension and are usually termed pro peptides or pro
sequences.

11. Intra molecular chaperones are classified into two groups on
the basis of their roles in protein folding.
The type I intra molecular chaperones mediate the folding of
proteins into their respective tertiary structures and are mostly
produced as the N-terminal sequence extension.
The type II intra molecular chaperones mediate the formation
of the quaternary or functional structure of proteins, and
usually are located at the C-terminus of the protein

12. Type I intra molecular chaperones.
Competitive inhibition: substrate (S) and inhibitor (I) compete for the active site.
It is suggested that the α-lytic protease folds through a nucleation mechanism, in
which the pro peptide folds first and acts as a scaffold that stabilizes the C-terminal
domain of the mature protease.
This allows for the structural arrangement of the two domains to pack into the native
structure. Sometimes the C-peptide has independent physiological functions. For
example, the C-peptide of pro insulin both stimulates Na+, K+-ATPase and functions
as an intra-molecular chaperone for folding of insulin.
Type II intra molecular chaperones
Intra molecular chaperones that are involved in the folding of the quaternary structure
of proteins are called type II intra molecular chaperones. The E. Coli K1-specific
bacteriophages contain tail spikes that exist as homo trimmers of endo-sialidases.
These tail spikes are produced with a C-terminal domain (CTD) that is not part of the
functional trimmer. The fact that the CTD folds independently from the enzymatic
domain and forms a hexa-mer suggests that the CTD is able to associate with each
other to initiate the tri merization of endo sialidases

13. Other categories
• Group I
• Group I chaperonins are found in bacteria as well as
organelles of endosymbiotic origin: chloroplasts and
mitochondria.
• The GroEL/GroES complex in E. coli is a Group I
chaperonin and the best characterized large (~ 1 MDa)
chaperonin complex.
• GroEL is a double-ring 14mer with a greasy hydrophobic
patch at its opening and can accommodate the native
folding of substrates 15-60 kDa in size.

14. Group II
• Group II chaperonins, found in the eukaryotic cytosol and
in archaea, are more poorly characterized.
• TRiC (TCP-1 Ring Complex, also called CCT for
chaperonin containing TCP-1), the eukaryotic
chaperonin, is composed of two rings of eight different
though related subunits, each thought to be represented
once per eight-membered ring. TRiC was originally
thought to fold only the cytoskeletal proteins actin and
tubulin but is now known to fold dozens of substrates.

15. Prokaryotic vs eukaryotic

16. Mechanism of
Chaperone Action
• Chaperonins undergo large conformational changes during a
folding reaction as a function of the enzymatic hydrolysis of
ATP as well as binding of substrate proteins and
cochaperonins, such as GroES.
• These conformational changes allow the chaperonin to bind an
unfolded or misfolded protein, encapsulate that protein within
one of the cavities formed by the two rings, and release the
protein back into solution. Upon release, the substrate protein
will either be folded or will require further rounds of folding,
in which case it can again be bound by a chaperonin.
• Step involved are

17. Step involved are
• Switch side of ATP binding each time
• Switch side of GroES binding for each folding
rxn
• Switch side of protein docking for each folding
rxns

18. The exact mechanism by which chaperonins facilitate
folding of substrate proteins is unknown.
According to recent analyses by different experimental
techniques, GroEL-bound substrate proteins populate an
ensemble of compact and locally expanded states that lack
stable tertiary interactions.
A number of models of chaperonin action have been
proposed, which generally focus on two (not mutually
exclusive) roles of chaperonin interior: passive and active.

19. mechanism
The free energy in form of ATP is used for
proper functioning

20. Probably the most popular model of the
chaperonin active role is the iterative
annealing mechanism (IAM), which focus
on the effect of iterative, and hydrophobic in
nature, binding of the protein substrate to
the chaperonin.

21. Example
The Hsp70 System
• The Hsp70 proteins constitute the central part of an ubiquitous
chaperone system that is present in most compartments of eukaryotic
cells, in eubacteria, and in many archaea.
• Hsp70 is comprised of two functional entities: an N-terminal ATPase
domain, and a smaller C-terminal peptide-binding domain.
• Hsp70 proteins are involved in a wide range of cellular processes,
including protein folding and degradation of unstable proteins The
common function of Hsp70 in these processes appears to be the
binding of short hydrophobic segments in partially folded
polypeptides, thereby preventing aggregation and arresting the
folding process DnaK and many other Hsp70 chaperones interact in
vivo with two classes of partner proteins that regulate critical steps of
its functional cycle

22. Steps
• The most important features of Hsp40 are that it binds to
peptides, and that it stimulates ATPhydrolysis of Hsp70.
• binding of substrate by both DnaJ and Hsc70 during
transfer
• double binding could change substrate conformation
• compress substrate (confinement)
• pull apart (partial unfolding)

23. Functioning cycle

24. implications
• pharmacology
• Molecular chaperone therapy is one of the latest pharmacological
approaches to lysosomal storage diseases. It fixes defective protein as
an alternative to Stop codon suppression treatment.
• These chaperones are minute molecules that can enter the central
nervous system ( via Blood Brain Barrier). Once in the CNS, they
attach to the enzyme (inactive form) and fix it so that it takes the
correct functional shape.
• Molecular chaperone-based vaccines offer a number of advantages
for cancer treatment. Pharmacological chaperones offer potential
advantages over competing approaches to treating genetic disorders,
including oral delivery and the ability to increase enzyme activity
levels in tissues that are hard to reach, such as the central nervous
system.

25. uses
• Cellular fusion vaccines were made to specifically target drug-
resistant cancer cells and tumour cell populations enriched in ovarian
cancer stem cells (CSC). Such vaccines showed enhanced capacity to
trigger T cell immunity to these resistant ovarian carcinoma
populations.
• The molecular chaperone heat-shock protein 70 (Hsp70) possesses
immune stimulatory properties that have been employed in the
preparation of anticancer vaccines. Hsp70 binds antigenic peptides in
the cytoplasm of cancer cells. Hsp70 thus serves as a convenient,
non-discriminating transporter of antigens and can protect the
peptides during internalization by APC and cross presentation to T
lymphocytes. We describe a method for purifying Hsp70-peptide
complexes that can be used to prepare molecular chaperone-based
vaccines, involving sequential gel filtration, ion exchange, and
affinity chromatography

26. Benefits

27. Conclusion
• I. Chaperones are protein in nature.
• II. Found mostly in all type of cells
• III. They have significant role in biological world
• IV. It action just like as law implications or care taker of a body.
• V. Beneficial in pharmacology, therapy, and important in central
dogma.
• VI. It is regulator of basic process of life.
• VII. They proceed voluntary as well as involuntary actions.
• VIII. Help in evolutionary studies.
• IX. Maintain life. Eg proteostasis is important for life.
• X. Some examples are
• Hsp40, Hsp70, Hsp90,GroE and substilin