L09-Protein_Misfolding - Part II Lecture 9 some proteins...

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30 Part II: Lecture 9 some proteins undergo assisted folding they don’t fold spontaneously by themselves the folding is facilitated by molecular chaperones proteins that interact with the partially folded or improperly folded polypeptides they facilitate correct folding by creating microenvironments in which correct folding can occur two classes of molecular chaperones have been studied well Hsp70 (heat shock proteins of Mr 70,000) o eukaryotic proteins o MW near 70,000 o more abundant in cells that are stressed by elevated temperatures o bind to regions of unfolded polypeptides that are rich in hydrophobic residues prevents aggregation “protect” the proteins that have been denatured by heat and those that are being synthesized block the folding of certain proteins that must remain unfolded until translocated across membranes chaperonins o elaborate protein complexes o required in the folding of a number of cellular proteins o an estimated 10-15% of E. coli proteins require the GroEL/ GroES system o first found when they were identified as being required for the growth of some bacterial viruses o unfolded proteins are bound within the GroEL complex which is transiently capped by GroES lids o GroEL undergoes a number of conformational changes driven by ATP hydrolysis coupled with the binding and release of GroES two other proteins have been found to assist in folding PDI (protein disulfide isomerase): catalyzes the interchange or shuffling of disulfide bonds until the native conformation is formed
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This note was uploaded on 11/28/2011 for the course CHEM 340 taught by Professor T.baird during the Fall '11 term at S.F. State.

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L09-Protein_Misfolding - Part II Lecture 9 some proteins...

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