Molecular Chaperones Quiz

Questions and Answers

What are the functions of molecular chaperones?

Bind exposed hydrophobic domains and prevent them from aggregating; assist in folding.

What are the 2 major classes of molecular chaperones?

Hsp70-type and chaperonin (TriC in eukaryotes and GroEL/GroES in bacteria).

What type of protein does not require chaperones at all?

Small proteins with no large hydrophobic regions.

Describe the structure of GroEL/GroES chaperonin in E.coli.

Two identical rings of 7 GroEL subunits, a cap composed of 7 GroES subunits, and a hydrophobic patch of amino acids inside the barrel opening of GroEL. Signup and view all the answers

Describe the folding cycle of GroEL/GroES chaperonin.

<ol> <li>Unfolded protein binds GroEL ring with 7 ATP. 2. Binding to GroES cap changes GroEL to cis conformation. 3. ATP is hydrolyzed to ADP. 4. Second unfolded protein binds the other GroEL ring with 7 ATP, causing first ring to release GroES cap, 7 ADP, and the better-folded protein. 5. Trans ring changes to cis form.</li> </ol> Signup and view all the answers

How do chaperones speed up the kinetics of folding? What are the two theories for how this occurs?

By reducing kinetically trapped intermediates. The theories are: 1. Iterative annealing - chaperone unfolds intermediate so it continues folding. 2. Confinement - controlled environment inside chaperonin smooths energy landscape for folding. Signup and view all the answers

Steroid receptors require what chaperone to put them in a conformation capable of binding hormones?

hsp90. Signup and view all the answers

Hsp90 client proteins are involved in many phenotypes displayed by cancer cells.

True Signup and view all the answers

What inhibits hsp90?

Geldanamycin (GM) and its derivatives (17-AAG and 17-DMAG). Signup and view all the answers

Study Notes

Functions of Molecular Chaperones

Bind to exposed hydrophobic regions of proteins, preventing aggregation.
Facilitate correct protein folding.

Major Classes of Molecular Chaperones

Hsp70-type chaperones.
Chaperonin chaperones: TriC in eukaryotes; GroEL/GroES in bacteria.

Proteins That Don't Require Chaperones

Small proteins lacking large hydrophobic domains do not need chaperone assistance.

Structure of GroEL/GroES in E. coli

Comprises two identical rings with seven GroEL subunits each.
Contains a cap made of seven GroES subunits.
Features a hydrophobic patch inside the GroEL barrel, crucial for recruiting unfolded proteins.

Folding Cycle of GroEL/GroES Chaperonin

An unfolded protein attaches to a GroEL ring, binding 7 ATP, allowing GroEL to connect with GroES cap.
The attachment of GroES induces a conformational change in GroEL to the cis state.
ATP molecules are hydrolyzed to ADP in the GroEL ring.
A second unfolded protein binds to the other GroEL ring (in trans state) with 7 ATP, leading to the release of the GroES cap and a better-folded protein from the first ring.
The trans ring subsequently changes to the cis state.

Kinetics of Protein Folding by Chaperones

Chaperones enhance folding kinetics by reducing kinetically trapped intermediates.
Theoretical mechanisms:
- Iterative annealing: Chaperones unfold intermediate states to promote further folding.
- Confinement: The controlled environment within chaperonins "smooths" the energy landscape for more efficient folding.

Steroid Receptors and Chaperones

hsp90 is required for steroid receptors to achieve a conformation that binds hormones effectively.

Hsp90 and Cancer Phenotypes

Hsp90 client proteins play significant roles in various cancer cell phenotypes.

Inhibitors of Hsp90

Geldanamycin and its derivatives (17-AAG, 17-DMAG) are known inhibitors of hsp90 activity.

Description

Test your knowledge on molecular chaperones and their functions with this quiz. Explore key concepts such as the major classes of chaperones and proteins that fold without assistance. Perfect for biotechnology students or anyone interested in molecular biology.