Molecule with reversible exothermic conformational change?

I proposed some exotic biochemistry on the Worldbuilding stack.
<https://worldbuilding.stackexchange.com/questions/166814/digestive-system-of-the-ultimate-omnivore/166829#166829>



> 
> Your creature oxidizes molecules in its "stomach" which is more of a
>  furnace. Anything that can be oxidized is fair game - any reduced
>  carbon, or nitrogen, or metal salt. Oxidation produces heat. The
>  amount of heat produced is controlled by controlling oxygen ingress to
>  the stomach.
> 
> 
> Under hot conditions, certain metalloproteins change configuration.
>  The circulation brings these proteins into hot conditions near the
>  stomach and they capture heat energy with the configuration change.
>  When the hot-configured metalloprotein circulates out to the cold
>  exterior (possibly radiator plates or fins) it shifts back to the cold
>  configuration. This conformational shift is linked to an ATPase and
>  generates ATP for the creature to use for its muscles and metabolic
>  processes, as Earth life does.
> 
> 
> 


I was challenged to produce a molecule which could capture and release energy in this way. Molecules do this all the time with a phase change - that is a steam engine. But is there any example of a molecule (or a whole type, perhaps) which undergoes a conformational change with heat that it later discharges in a controlled manner, with an exothermic relaxation back to the cold conformation. Not necessarily a biomolecule. 


