Membrane Biogenesis

Transbilayer Organization and mobility of phospholipids in normal and pathologic erythrocytes. Lipid localization and mobility in the plasmalemma of the aortic endothelial cells are reversibly affected by the presence of cell junctions. Phospholipid dynamics in membrane biogenesis in hepatocytes. The regulation of phosphatidylcholine synthesis at the subcellular level in Krebs II ascite cells. Factors which may alter the assembly of biomembranes so as to influence their structure or function. F.A.Kummerow Myocardial cell death and the possible role of sarcolemmal phospholipids (based on morphological observations). The role of mitochondrial membrane phospholipid polar headgroups in yeast cytochrome c oxidase kinetics. Interaction of the bibenzimidazole derivative Hoechst 33258 with lipid bilayers-a fluorescence study. Interaction of the mitochondrial precursor protein apocytochrome c with modelmembranes and its implicaüons for protein translocation. The assembly and transfer of Oligosaccharide chains to proteins. WJ.Lennarz 287 Sequence determinants of protein sorting into and across membranes. G.von Heijne 307 Components involved in protein translocation across the membrane of the endoplasmic reticulum. B. Dobberstein 323 Import of small secretory and plasma membrane proteins into the endoplasmic reticulum. 337 Biogenesis and membrane topology of outer membrane proteins in Escherichia coli. J.Tommassen 351 What can we learn from colicins about the dynamics of insertion and transfer of proteins into and across membranes. The use of hybrid proteins in the study of protein targeting Signals. Pullulanase: a new specific secretion pathway in Escherichia coli. A genetic analysis of pullulanase export from Klebsiella aerogenes. 429 Cloning of xcp genes possibly involved in protein secretion in Pseudomonas aeruginosa. Vacuole division and inheritance in Saccharomyces cerevisiae. SUMMARY We are employing precursors of small secretory and plasma membrane proteins as tools for defining the different stages in the import of proteins into the endoplasmic reticulum (ER). The precursor proteins that we selected are M13 procoat protein, the precursor of a bacterial plasma membrane protein, and the precursors of two eucaryotic secretory proteins, honeybee prepromelittin and frog prepropeptide GLa. Our experimental Systems involves in vitro Systems, suitable for translation as well as import of the translation produets into microsomes. The following stages in import can be resolved: i) Specific association of a precursor protein with the ER-membrane; ii) Insertion of a precursor protein into the ER-membrane; and iii) Assembly of a protein into the ER-membrane and transport of a protein across the ER-membrane, respectively. We present a working model for the import of small precursor proteins into ER.