Proteomics is the large-scale study of proteins, particularly their structures and functions. This term was coined to make an analogy with genomics, and is often viewed as the "next step", but proteomics is much more complicated than genomics. Most importantly, while the genome is a rather constant entity, the proteome is constantly changing through its biochemical interactions with the genome. One organism will have radically different protein expression in different parts of its body and in different stages of its life cycle.

The entirety of proteins in existence in an organism throughout its life cycle, or on a smaller scale the entirety of proteins found in a particular cell type under a particular type of stimulation, are referred to as the proteome of the organism or cell type respectively.

With completion of a rough draft of the human genome, many researchers are now looking at how genes and proteins interact to form other proteins. A surprising finding of the Human Genome Project is that there are far fewer genes that code for proteins in the human genome than there are proteins in the human proteome (~22,000 genes vs ~200,000 proteins). The large increase in protein diversity is thought to be due to post-translational modification of proteins.

To catalogue all human proteins and ascertain their functions and interactions presents a daunting challenge for scientists. An international collaboration to achieve these goals is being co-ordinated by the Human Proteome Organisation (HUPO http://www.hupo.org ).

Key technologies for proteomics

• 1-D electrophoresis and 2-D electrophoresis are for the separation and visualisation of proteins.
• To identify and characterise proteins mass spectrometry, X-ray crystallography, and NMR are used.
• To characterise protein-protein interactions, a number of chromatography techniques are used especially affinity chromatography . Protein expression systems like the yeast two-hybrid and fluorescence resonance energy transfer (FRET) can also be used to characterise protein-protein interactions.

Databases

• PIR
• Swiss-Prot
• Pfam

External links and sources

• In 2004 the estimated number of genes in genome dropped from 33,000 to 20,000-25,000 http://web.mit.edu/newsoffice/2004/humangenome.html

Topics within genomics

Genome project | Glycomics | Human Genome Project | Proteomics | Structural genomics

Bioinformatics | Systems biology