BIOLOGY 2B03 Lecture Notes - Lecture 1: Groes, Endoplasmic Reticulum, Groel
17 Sep 2018
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Chaperones: 1) monomeric molecular chaperones & 2) multimeric chaperonin complex. Hsp70 found in cytosol and mitochondria of eukaryotic cells. Hsp70 = "heat shock proteins" = expressed at high levels when stress = i. e. elevated temperature. @ higher temperatures (where proteins can denature) = cell makes heat shock proteins which help to refold denatured proteins. Substrate = unfolded protein that is leaving the ribosome. A cluster of hydrophobic residues on the substrate is exposed to the aqueous cytosol. Then hsp70"s hydrophobic patches (residues) then bind on the unfolded proteins (atp + h20) + dnaj/hsp40 ---grpe/bag1---> adp + p. It is the hydrolysis from atp to adp that changes the conformation of the hsp70 chaperone = allows the unfolded protein to fold properly. Then new atp comes in to the fill the nucleotide-binding domain. Hsp70 is ready binds to another unfolded protein. Nucleotide binding domain (atp + h20) --> adp + p = hydrolysis. "substrate" = the unfolded protein from the ribosome.
