lecture0203audio - 2) Unfolded polypeptide enters GroEL...

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Molecular Chaperones First isolated as “heat-shock”  proteins in many organisms –  increase protein expression after a  heat shock. Then as bacterial proteins which  catalysed assembly of viral coats Then began to be found to be  present in all cells, promoting the  assembly of proteins and protein  complexes.
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Molecular Chaperones GroEL/GroES – an example from a  bacterium GroEL – a huge complex of 14 subunits  arranged in two stacked rings “a double  doughnut” – forming 2 chambers with  interiors lined with hydrophobic R-groups GroES – smaller, 7 subunits – forms a  cap on each end of the doughnut Attachment of GroES to GroEL causes a  massive conformational change that  expands the space in the GroEL  chamber
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EP Figure 4 1) Unfolded polypeptide has hydrophobic R- groups (unfavourably)  facing the surrounding aqueous  Environment
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Unformatted text preview: 2) Unfolded polypeptide enters GroEL chamber, and snugly binds to its hydrophobic interior lining. 3) GroES and ATP is bound. ATP is consumed and GroEl chamber expands. Polypeptide is now exposed to a more aqueous environment and correct folding, is favoured, with hydrophobic groups buried in the polypeptides interior 4) ADP is released, GroES detaches. Correctly folded protein is released Molecular Chaperones Note that chaperones do not determine the final structure of the folded protein that is determined by the lowest energy state of the primary structure of that protein in its native environment. They simply speed up the folding of the protein by constraining it and providing the right environment Many proteins do not require chaperones to fold...
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This note was uploaded on 05/11/2010 for the course BIOLOGY 105 taught by Professor Richard during the Spring '10 term at George Mason.

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lecture0203audio - 2) Unfolded polypeptide enters GroEL...

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