Proteasome

From Palaeos

A proteasome is the evil twin of a chaperonin. Like a chaperonin, it is a longitudinally symmetrical series of 7-member rings (but four rings, not two) with a hole through the middle and an affinity for improperly-folded polypeptides. Unlike a chaperonin, a proteasome does not restore proteins to conformational health and send them on their way. Instead, the proteasome slashes the doomed polypeptide into little 7-13 amino acid oligopeptides so that they may be completely degraded by other proteases. Since its function is reclamation, not rehabilitation, a proteasome lacks any of the bells and whistles of a chaperonin and possesses a much narrower aperture. Thus, only proteins which are more or less completely unfolded can pass into the destructive core of the complex. The basic 20S proteasome is found in Actinobacteria and Archaea. In eukaryotes, the 20S structure forms the core of a 26S proteasome.

Credit

ATW?