Proteomics, which is generally defined as the characterization of the complete protein complement of a cell, tissue, or organism (a proteome), has moved to the forefront of "big science" now that the complete genomes of several organisms--including man--have been sequenced.1 But why is proteomics important? Simply put, proteins define the function of cells, tissues, and even organisms. Every cell in the human body contains an equivalent set of genes, but not every cell expresses the same ones. Only B cells, for example, express immunoglobulins. In addition, each gene can give rise to multiple proteins, either through alternative splicing or post-translational modifications. Finally, there is no direct correlation between mRNA abundance and steady-state protein levels.2 For all of these reasons, the field of proteomics is booming.
Brian T. Chait is the director of the National Resource for Mass Spectrometric Analysis of Biological Macromolecules at Rockefeller University, one of several National Institutes ...
