Not such a dismal science: the economics of protein synthesis, folding, degradation and antigen processing

There is a pronounced tendency among cell biologists to focus on qualitativ e aspects of cell physiology. The remarkable accomplishments of evolution i n creating cells can only be fully appreciated, however, by combining this qualitative analysis with a quantitative assessment of cellular constituent s and processes. Here, I consider the overall protein economy of cells as i t relates to recent advances in understanding protein folding, ubiquitin-ta rgeted proteasome-mediated degradation of proteins and the generation of pe ptide ligands for major histocompatibility complex (MHC) class I molecules.