Protein folding in the cell: molecular chaperones pave the way.

In vitro, many unfolded polypeptides are able to fold to the native state spontaneously, indicating that the amino acid sequence of a protein contains all the information necessary to specify its three-dimensional conformation. It had been assumed that protein folding in vivo also generally occurs in a spontaneous process. This view has changed only recently due to the discovery of a number of proteins, now commonly called 'molecular chaperones', which are essential for cellular protein folding and occur ubiquitously in eubacteria, archaebacteria and in eukaryotic cells.