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Monday, December 15, 2008

Chaperones groups of proteins assist in the folding of other proteins

Question 32
Which of the following groups of proteins assist in the folding of other proteins?
1. Proteases.
2. Proteosomes.
3. Templates.
4. Chaperones
Answer
4. Chaperones
Reference
Harper 27th Edition Pages 37, 515,
Textbook of Medical Biochemistry 4th Edition Chaterjee and Shinde Page 225
Quality
Spotter
Status
Repeat
QTDF
All books give this
Discussion
The chaperones are proteins that play a role in the proper folding of other proteins without themselves being a compound of latter. They stabilize unfolded or partially folded intermediates, allowing them to fold properly and prevent inappropriate interactions. Few substances that can be called as chaperones include
a.       Calreticulin
b.      HSP 90A (Heat Shock Proteins)
c.       Synuclein alpha
d.      Lectin mannose binding 1
e.       DNA fragmentation factor 45
f.        Tubulin specific chaperone C
g.      Arylhydrocarbon-interacting receptor protein-like 1
h.      Tubulin specific chaperone D
i.        Unactive progesterone receptor 23KD (Yeah, That the name given - it is not printing mistake)
Explanation
1. Proteases are enzymes that hydrolyze proteins.
2. Proteosomes (especially the 26S component) help in degrading the proteins that are “marked” with Ubiquitin.
3. Template is involved in Synthesis of Nucleic Acids.
4. Chaperones are involved in Protein folding
Comments
Chaperonins are hsp60 family of chaperons
Tips
Few more points about Chaperones
1)      Present in many species
2)      Few are induced by conditions which cause unfolding of newly synthesized proteins
3)      Bind predominantly to Hydrophobic regions
4)      Act as Editing Mechanisms or Quality control
5)      Most have ATPase activity
6)      Found in
a)      Cytosol
b)     Mitochondria
c)      Lumen of Endoplasmic Reticulum

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