Why is it that when you denature protein that's it?

[scilearner]

Hello everyone,

 

Why is that when denature protein you can't get it back to orginal shape. Practically it is obvious that when you burn something it is not going to come back for original shape but what is the chemical basis behind this. Are molecules loss or, heat loss or why is it this so. Why does extreme cooling can not get it back to orginal shape. Thanks

[cypress]

Proteins are constructed and generally folded in the cell aided by various molecular machines to form the intended configurations. Without support of systems that can reproduce the effects of these molecular machines, it is rarely possible to restore the proteins after being denatured.

[ewmon]

When the proteins denature, they usually aggregate (ie, stick to one another) after twisting and distorting. This happens, for example, when you add vinegar to milk. The proteins not only distort (ie, expose their hydrophobic "innards"), but they fall out of solution and aggregate ... they form curds. You can flush the acidic vinegar/whey solution out of the curds and put them in fresh milk, but they will remain mostly aggregated.

 

Protein conformation is perhaps the main reason why animals maintain what is called "physiological conditions" (pH, temp, salinity, etc). For example, proteins begin unfolding above 40°C/104°F.

[CharonY]

It actually depends on the kind of denaturation. Essentially, it is based on the fact that proteins often have several stable states that they can arrange themselves under a given condition. Chaperones do indeed play a role by e.g. leading the protein to a particular stable conformation or, in other cases allow them get to that state at all (as it would not happen spontaneously due the requirement of additional energy). If chaperones are involved in the correct folding, obviously the renaturation won't happen easily (thought there are in fact stress-related chaperones whose main function is to renature proteins).

However, in some cases removing the denaturant the proteins are able to retain their original confirmation.