ABSTRACT
The proteome is the collection of protein molecules present in a cell. The proteome is therefore the final link between the genome and the biochemical capability of the cell, and characterization of the proteomes of different cells is one of the keys to understanding how the genome operates and how dysfunctional genome activity can lead to diseases. Transcriptome studies can address these issues only in part. Examination of the transcriptome gives an accurate indication of which genes are active in a particular cell but gives a less accurate indication of the proteins that are present. This is because the factors that influence protein content include not only the amount of mRNA that is available but also the rate at which the mRNAs are translated into protein and the rate at which the proteins are degraded. Additionally, the protein that is the initial product of translation may not be active, as some proteins must undergo physical and/or chemical modification before becoming functional. Determining the amount of the active form of a protein is therefore critical to understanding the biochemistry of a cell or tissue.
