BIOLOGY 2B03 Lecture Notes - Lecture 3: Ubiquitin, Covalent Bond, Cysteine
Document Summary
If a protein cannot be folded, it forms aggregates in the cell which are detrimental to the cell and are thus recognized for degradation in the proteasome. Both molecular chaperones and chaperonins assist in protein folding by: preventing incorrect folding, preventing incorrect associations with other proteins. These mechanisms are seen in all organisms and are not specific to certain types of proteins. They bind to hydrophobic amino acid residues on a polypeptide and prevent the protein from forming incorrect folds due to hydrophobic interactions within an aqueous environment within a protein or with other proteins. An example of a chaperone protein are heat-shock proteins (hsp) which are expressed in high levels when under conditions of stress such as high temperatures. This is because high temperatures cause proteins to denature and unfold so these chaperones are expressed in high levels to refold various proteins in the cell. Hsp(cid:1011)0 is a(cid:374) e(cid:454)a(cid:373)ple a(cid:374)d it s fou(cid:374)d i(cid:374) c(cid:455)tosol a(cid:374)d (cid:373)itocho(cid:374)dria.
