Perhaps the most appropriate definition of proteomics is "any large-scale or systematic characterization of the proteins present in a cell, tissue, or organism." It is a different paradigm from conventional reductionistic scientific investigations that typically focus on a single gene or protein. Proteome research asks unbiased biological questions such as what protein levels or activities change between two experimental conditions.
Although sequencing the human genome was initially daunting, it was a finite problem with a specific endpoint. In contrast, the proteome of any organism is highly dynamic with an endless number of possible variations. Even the proteomes of prokaryotes and the single-cell eukaryote yeast are essentially infinite because, in addition to changes during normal development, growth, and cell division, their proteomes respond in biologically important ways to environmental changes. Hence, there is no discrete proteome, per se, even for simple single-cell organisms.
For most of us engaged in proteome research, ...
