Published by Australian Academy of Science
Biology meets industry – genomics, proteomics, phenomics Box 1 | Unveiling the proteome

If sequencing the human genome was a massive undertaking, consider some of the challenges involved in creating a map of the human proteome:

Firstly, there are far more proteins in an organism than there are genes. Part of the reason for this is that messenger RNA (mRNA), the mobile copy of DNA which is used as a template when a cell creates a protein, can undergo 'editing' after it is first copied. Segments of the RNA can be removed before a protein is created from it, meaning a number of different proteins can be created from the same gene. Even after the protein has been translated from the mRNA it can still undergo numerous transformations including the addition of chemical groups, the removal of sections of the protein, and combination with other proteins – any of which can alter the form and function of the finished molecule. An extreme example is a fruit fly gene which was discovered by scientists to code for 38,000 different proteins! So while we now know that humans have approximately 30,000 genes, our total number of proteins is still unknown – although estimates put the total at 100,000 or more.

Secondly, while the genome remains relatively static in any given cell in an organism, the expression of the proteome changes from cell to cell and from moment to moment. Age, gender, health, and recent consumption of food or drugs all affect the proteome – the same cell, if examined at different times or under different conditions, can be expressing a different complement of proteins.

Thirdly, cells from different tissues within the same organism express distinct sets of proteins.

These and other factors involved in making a map of the human proteome present a challenge worthy of the potential rewards it might offer.

Related sites

• Proteins are the body's worker molecules (National Institutes of Health, USA)

• Drug Discovery and Biotechnology Trends – Proteomics I: In pursuit of proteins (Science, USA)

Other boxes

Box 2. Case study – Remicade and Glivec