HOULIHAN, D.F; MARTIN, S.A.M.; University of Aberdeen: Protein metabolism in fish; gambling on proteomics.

Protein metabolism in animals involves a balance between protein synthesis and degradation resulting in net gain or loss of proteins in an organism. Although protein synthesis is stimulated by feeding and growth is correlated with an increase in protein synthesis, rates of protein degradation appear to play a key role the efficiency with which fish deposit synthesised protein. For example, within a species individuals with similar rates of protein synthesis may have widely different growth rates because of differences in protein degradation (i.e. turnover). Proteome analysis has been utilised to identify changes in individual proteins in fish that have been challenged by dietary changes, resulting in altered protein metabolism. The proteome is the expressed protein complement of a genome in a tissue. Protein extraction followed by high resolution 2 dimensional electrophoresis, coupled with gel image analysis allows hundreds of protein to be monitored in parallel, permitting a global picture to emerge of changes in protein profile under different metabolic states. A rainbow trout proteome map is being developed in which all proteins are recorded in terms of molecular weight, isoelectric point (pI) and abundance. Protein spots that are found to be of interest are excised from the gel and subjected to trypsin digestion and separation of peptides by mass spectrometry, results are used to search the Genbank data base. Results from two experiments will be presented, firstly the protein profile changes brought about by starvation, and secondly the use of plant derived proteins in the diet. Proteomics can be coupled with labelling techniques to obtain rates of synthesis of individual proteins. In conclusion we demonstrate how proteomics coupled with genome characterisation could help understand protein metabolism in fish.