ABSTRACT
It was announced in 2001 that the human genome had been sequenced, thus heralding a new era for biological research.1,2 However, the sequenced genome didn’t provide information about protein species in cells and tissues. Consequently, focus then shifted to the intricate interactions and roles of proteins in cells-that is, to a new fi eld called proteomics. Proteomics by defi nition is the systematic determination of protein sequence, quantitation, modifi cation state, interaction partners, activity, subcellular localization, and structure in a given cell type at a particular time.3 There are an estimated 30,000 to 40,000 human genes. However, the old canonical defi nition of “one gene, one protein” is no longer valid. One gene does not necessarily produce one protein. Many genes are made up of a series of substructures, or exons, that can be combined in different ways to give rise to a diverse series of similar proteins that have distinctly different functions. Once proteins are made, many of them can be modifi ed by phosphate, carbohydrates, or lipids with different structural confi gurations, thus adding to the complexity to understanding the
action and relationship of proteins. A comparable study of the protein version of the genome, the proteome, must deal with approximately 30,000 genes that can be rearranged to yield the more than 800,000 proteins, which can then be modifi ed with over 300 different submolecular entities.
