Cover Picture

Abstract

The cover picture shows two features from the complex area of protein targeting in eukaryotic cells. The upper image illustrates the recruitment of the signal peptidase complex (SPC; light blue) and the oligosaccharidyl transferase complex (OST; green) to the ribosome–nascent polypeptide chain–Sec61 complex in the endoplasmic reticulum (ER) membrane. SPC endoproteolytically removes the signal peptide, OST attaches core oligosaccharides to the translocating nascent chain. The lower image shows other systems for protein translocation across distinct cellular membranes that work on principles similar to those first established for the ER (bold blue arrow). The slim blue arrows indicate the related systems within the mitochondrial matrix and the chloroplast stroma. Bold and slim red and green arrows indicate protein translocation systems for import across the outer and inner mitochondrial or chloroplast membrane, respectively. White and black arrows indicate transport into and out of the nucleus, respectively, across the nuclear pore complex. Further details are given in the Nobel Lecture by G. Blobel on p. 86.