[The 1999 Nobel Prize for physiology or medicine].
It has been awarded to Günter Blobel, for a so-called signal hypothesis. In this research Günter Blobel has proven that information about the final localization of a protein in the cell is given in its sequence. Such a targeting signal can be either cut off (presequence) or can be localized within the final sequence of a protein. The mechanisms responsible for secretion, the movement of proteins to or from nucleus, and guiding of proteins to mitochondria, chloroplasts and peroxisomes have been described. In particular, proteins involved in interactions with the signal sequences were reviewed. The channels responsible for transfer of polipeptides through the membranes were also presented. A contribution of Günter Blobel and his coworkers in the foundation and development of a new field of research on protein guidance has been emphasized.