RAPID IDENTIFICATION OF YEAST PROTEINS ON 2-DIMENSIONAL GELS

This work describes a rapid and sensitive technique for the identifica tion of Saccharomyces cerevisiae proteins on two-dimensional gels base d on the determination of their amino acid ratios. Specific double lab eling with H-3 and C-14 or S-35-labeled amino acids, chosen among thos e that are specifically incorporated into proteins without interconver sion, allowed an accurate measurement of different amino acid ratios f or 200 proteins. A computer program was developed to screen a yeast da ta base containing 1700 protein sequences and to identify proteins mat ching the measured M(r), pI, and amino acid ratios. The method, tested with 45 reference proteins, allowed 79 new identifications correspond ing to abundant proteins belonging to a few functional families. Some protein spots correspond to homologs of mammalian proteins or to uncha racterized open reading frames. Remarkably, among identified proteins of similar abundance, the organellar proteins have a markedly lower co don usage bias than the cytosolic ones. The double labeling technique is particularly suited to the analysis, on a single two dimensional ge l, of the influence of physiological or genetic changes on yeast prote in content.