Molecular Chaperones Report

MOLECULAR CHAPERONES

Group 5 – A2Capacio, Diane Chloe

Cardeño, Sheree Ann Rachille

Casem, Princess Joy

Casteñeda, Felix II

Castro, John Michael

Ceneta, Raymond

INTRODUCTIONChaperones Proteins which assist in protein folding Assists in the translocation of polypeptide

chains Multiprotein assembly and disassembly Escort some proteins to specific

destinations Rescue proteins trapped in misfolded

dead-ends (folded in their hydrophobic regions)

During the synthesis of proteins, parts of it already begin folding

The instruction on the sequence’s proper folding is dependent on the amino acid sequence itself

Protein folding

Protein folding

Most of the hydrophobic amino acids are buried inside the structure (core)

Some proteins already fold as it comes out of the ribosome in a matter of seconds, forming what is called a molten globule

Chaperones assist in folding of some proteins


They are of much help since there are a number of pathways at which the protein can achieve its final form from an unfolded state

Many of these chaperones are termed heat shock proteins because they are made in abundance at an elevated temperature (~42oC for cells normally at 37oC)


A feedback-like system is made in this setting, since an increase in unfolded proteins resulting from an increased temperature will eventually lead to the synthesis of chaperones


Some of the major chaperone families include Hsp60 and Hsp70, which functions at different organelles

The mitochondria have its own set of Hsp60 and Hsp70 proteins which are distinct from those found in the cytosol and BIPs (special types of Hsp70) in the endoplasmic reticulum

Chaperones assist in folding of some proteins Hsp70s act early in the synthesis of the

protein before that protein leave the ribosome

Hsp60s, however, acts on the fully synthesized protein by forming a barrel-like structure. Hsp60s are also termed as “Chaperonin” and they have what is called an “isolation chamber” where the misfolded protein is fed into


Chaperones use a series of ATP hydrolysis in aiding a protein to fold correctly

How does the cell recognize misfolded proteins?

Usually, when a hydrophobic region is at the protein globule surface, it is considered abnormal

Presence of these kinds of proteins may render, not only nothing for the cell, but also danger. Aggregations of misfolded proteins may result to some known severe human diseases

Types of Molecular Chaperones

Folding Holding Those that increase solubility of proteins

Role in protein assembly

They guide in the proper folding of proteins

Misfolded proteins are allowed to refold into their correct conformation by having a suitable environment which is provided by the chaperones, chaperonins in particular

Refolding of denatured proteins

In a study involving recombinant HSP17 of Synechocystis sp., malate dehydrogenase which underwent denaturation made complexes with HSP17 which then functioned as a storage of the unfolded protein, and later on transported to the network of Dnak/DnaJ/GrpE and GroEL/ES chaperones for eventual refolding (Török etal., 2001)

Production of recombinant proteins

In a study using E. coli, overproduction of bacterial chaperones, GroEL and GroES, via genetic engineering resulted to high yield of recombinant human protein-tyrosine kinase p50csk which are in an insoluble forms within the bacterial cell.

Production of recombinant proteins

Overproduction of these chaperones resulted in the subsequent dissolution of the protein kinase and enabled its purification (Amrein et al., 1995)

Production of cancer vaccines HSPs which are derived from a

particular tumor has been known to bring on immunity against the tumor where came from that tumor. Vaccines of this kind are effective on different types of tumors and can bypass the need for identifying the responsible peptide which causes the immunity

Production of cancer vaccines

These vaccines are specific for the tumor and for the patient because they confine the identity of the tumor cell. HSP96 has already been studied with a number of cancer illnesses such as, melanoma, renal cell carcinoma, gastric cancer, pancreatic cancer, low-grade lymphoma, colorectal cancer and chronic myelogenous leukemia (Oki and Younes, 2004)

Possible causes of Protein Misfolding

•Genetic Mutation•Increased Heat Production

Properties of Chaperones

•Present in a wide range of species from bacteria to humans•Many are so called Heat Shock Proteins•Some are inducible by conditions that cause unfolding of newly synthesized proteins

•They bind to predominantly hydrophobic regions of unfolded proteins and prevent their aggregation•They act in part as quality control•Associated with ATPase activity•Found in cytosol, mitochondria and lumen of ER

Activation of Chaperones

Rely on ATP-driven conformational change

Most of the hydrophobic amino acids are buried inside the structure (core)

Holding Chaperones Maintains partially folded protein

on their surface to await availability of folding chaperone upon stress abatement

Chaperons w/c Promotes Solubility of Protein

Aggregates as a result of stress

2 Major Types of Molecular Chaperones Hsp 6O

Also called Chaperonin

Barrel like structure- where unfolded

protein is retained, giving it time &

suitable env’t to fold properly

Hsp 7O

These protein acts early, recognizing small strech of hydrophobic amino acid pn a protein surface

GroEL-GroES System

It is a bacterial chaperone belong to Hsp 6O family

It is a hollow cylinder consist of 2 seven subunit rings stacked back to back

Dnak Chaperones

They are chaperones of host protein, refolding, translocation and general mngt of deleterious effest of stress

They are under the hsp70 family

Hsp33

Also know as REDOX-ACTIVATED HOLDING CHAPERONES

It is a redox regulated chaperon that stabilized protein unofolded by severe oxidative stress

Hsp31

Also known as Managing Heat & AcidStress

It fxn as a holding chaperons that helps cell handle protein unfolding under extremes of temp.

Plays role in ability of strved E. Coli to survive in a acid stress

Clp Disaggregase

Belong to hsp100 family w/c role is to degrade unfolded/misfolded protein or to stabilized and reactivate aggregate proteins

PROSPECTIVE THERAPEUTIC RATIONALES THAT INVOLVE

CHAPERONES

Drugs targeting specific Chaperone Activities

1. Immunophilinsa. Immunosuppressants cyclosporin A

and FK506• Transplantation procedure,

autoimmune and inflammatory diseases.

• Useful as neurotrophic agents.

2. HSP70a. DSG interact selectively with HSP70

class chaperones• Potent immunosuppressive agent.• Maybe able to reverse renal

allograft rejection episodes.• Maybe quite useful in combination-

therapy.• Further studies required.

3. HSP90• Inhibitors of signal transduction • Examples are GA and

benzoquinone ansamycins which are potential as anti cancer agents

Induction of protein and chemical chaperones

Injury protection

•Induction of heat shock response might be an effective prophylactic treatment to minimize myocardial injury.

•Herbimycin which induce activation of HSF1 has been shown to protect cardiomyocytes in culture.

ReferencesCampbell, NA, JB Reece, LA Urry, ML Cain, SA Wasserman, PV Minorsky and RB

Jackson. 2008. Biology 8th ed. Pearson Benjamin Cummings, CA

Alberts, B, A johnson, J Lewis, M Raff, K Roberts and P Walter. 2008. Molecular Biology of the Cell 5th ed. Garland Science, UK

Amrein, KE, B Takacs, M Steiger, J Molnos and P Burn. 1995. Purification and characterization of recombinant human p50csk protein-tyrosine from an Escherichia coli expression system overproducing the bacterial chapreones GroES and GroEL. Proc. Nat. Acad. Sci. 92(4):1048-1052.

Török, Z, P Goloubinoff, I Horvath, NM Tsvetkova, A Glatz, G Balogh, V Varvasovszki, DA los, E Veirling, JH Crowe and L Vigh. 2001. Synechocystis HSP17 is an amphitropic protein that stabilize heat-stressed membranes and binds denatured proteins for subsequent chaperone-mediated refolding. Proc. Nat. Acad. Sci. 98(6):3098-3103.

Oki, Y and A Younes. 2004. Heat shock protein-based cancer vaccines. Expert Review of Vaccines 3(4):403-411.

http://faculty.washington.edu/baneyx/Chaperones/Chaperones.html

Smith, D, L Whitesell and E Katsanis. 1999. Molecular Chaperones: Biology and Prospects for Pharmacological Intervention. Pharmacological Reviews 50(4): 493-514.

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Molecular Chaperones Report