The intent in initiating this volume was to bring together a series of essays which would define our present understanding of the endosome and lysosome and their interrelationship. The editors deliberately encouraged the contributors to be speculative; to strive to put order to the -real- world of incomplete and sometimes conflicting data. Seeing science from the laboratory bench can often be like viewing an impressionistic painting from up close; a series of paint dabs with no apparent order. The contributors to this volume were asked to step back and leave the reader with a sense of the...

The incentive for putting together Volume 4 of this series was to review the wealth of new information that has become available in prokaryotic organisms in protein export and membrane biogenesis. Just in the last several years, protein translocation has now been efficiently reconstituted using defined components and the mechanism by which proteins are moved across membrane bilayers is now being examined at a higher resolution. In addition, because of a new technical breakthrough using osmolytes, it is now possible to reconstitute a number of channel proteins, ATPase, receptors, and...