This book highlights proteasome structures and how they are related to different aspects of proteasome function. Moreover, the book reports on the functional roles these highly developed proteolytic machines play within the cell. It was a great surprise to the scientific world that proteolysis provides crucial functions in cellular regulation. The surprise was even greater when it was found that not lysosomes, but protease complexes with remarkably sophisticated architectures were responsible for the control of essential regulatory events. Excitingly, proteasomes were found to be involved in widespread functions of cell physiology, which included degradation of protein waste, antigen presentation, regulation of cell metabolism and cell differentiation as well as control of the cell cycle. The discovery of such multiple and essential functions made investigation of proteasome mediated regulatory proteolysis a highly significant theme in cell biology. Written by pioneers in the field the book represents a comprehensive up-to-date view on proteasome structures and functions from the ultimate frontier of cell biology research. It ties the reader to all facets of cell function. This work is an indispensable source for scientists working in the fields of basic and applied cell biology and immunology. Different aspects of proteasome functions are associated with the development of detrimental diseases like cancer, neurodegeneration, cystic fibrosis or immune disorders. Therefore, data reviewed in this book are important for physicians and pharmacologists active in research, and experts in the pharmaceutical industry.