Protein Identification in Proteome Projects

Abstract

Two-dimensional gel electrophoresis in its modern form was described in 1975 (O’Farrell 1975; Klose 1975). Even the earliest papers showed that thousands of proteins could be resolved on a single gel, and that qualitative differences between samples could be detected. Researchers excitedly commented that such gels potentially represented a means of investigating global processes in living systems. However, in many ways the invention of 2-D separation was ahead of its time. For example, molecular biology was in its infancy. The cloning of cDNA had just been described (Rougeon et al. 1975), but methods like Sanger DNA sequencing (Sanger et al. 1977) or the polymerase chain reaction (Saiki et al. 1985) were unknown. By contrast, protein sequencing by Edman degradation had been defined and automated (Edman and Begg 1967) but still required hundreds of picomoles of protein — at least an order of magnitude more than that purified on a 2-D gel. The consequence of the above factors was that protein and DNA sequence was only available for a handful of proteins. The first genome sequence was still 20 years away! So whilst in 1975 2-D gels could separate a sample into thousands of components, and could perhaps describe interesting phenomena in terms of spots on a gel, without protein identification these gels remained little more than a tool of description or classification.