In prokaryotes, the polypeptide chains in which proteins are synthesized only tend to fold into their final, operational form when the chain is complete. In eukaryotes, by contrast, individual domains of a single protein can fold sequentially and independently. This striking finding can help to resolve the puzzle of why prokaryotes tend to rely much more heavily on chaperonin- assisted protein folding than do eukaryotes, but the molecular mechanisms underlying the different treatment of nascent polypeptide chains remain to be defined.
