Analysis - "New Jobs For Ancient Chaperones

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New Jobs for Ancient Chaperones "New Jobs for Ancient Chaperons" by Pramod K. Srivastava. Pg 50, July 2008, Vol 299, Number 1 Heat shock proteins (HSP) are produced in response to stressful conditions including heat. HSPs help cells with coping by keeping cellular processes working smoothly. They play a key role in immune defenses against cancer and other pathogens. HSPs act as chaperones for other proteins and have two objectives: “Inhibit undesirable protein interactions and promote desirable protein interactions in order have stable bonds form between proteins”. HSPs bind to various proteins to perform a range of jobs by way of helping newly formed polypeptides to fold into their proper shape, disassembling polypeptides if they have been damaged and also chaperoning proteins to their intended associating proteins and keeping them from other interfering cellular processes and/or proteins. Primary role of HSPs: Keeping order is one way that HSPs maintain their key role of chaperoning other cellular proteins, guarding them from going astray. Two major families of molecular chaperones are HSP60 family and HSP70 family. HSP60 family (chaperonins): resembles a cage and has a highly hydrophobic inner rim that attracts amino acids with exposed hydrophobic regions of an unfolded protein to bind to it. The inside of the cage is hydrophilic which the hydrophobic amino acids don’t work well with, therefore; the trapped molecule is forced to change shape to its correct conformation. HSP70 family: in contrast to HSP60 grab their substrates instead by the “elbow” so to speak to chaperone them along. HSP70 has a peptide-binding cleft which is open when HSP70 is bound to the ATP, as the ATP undergoes hydrolysis and becomes ADP the cleft closes and the polypeptide in the HSP70 is then folded to its correct conformation.

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