Dynamic (13) C-labelling experiments prove important differences in protein turnover rate between two Saccharomyces cerevisiae strains

Artikel i vetenskaplig tidskrift, 2012

We developed a method for quantification of protein turnover using (13) C-labelled substrates combined with analysis of the labeling pattern of proteinogenic amino acids. Using this method the specific amino acid turnover rates between proteins and the pool of free amino acids were determined for eight different amino acids (alanine, valine, proline, aspartic acid, glycine, leucine, isoleucine and threonine) in two Saccharomyces cerevisiae strains (CEN.PK 113-7D and YSBN2). Furthermore, proteasome activities were compared for both strains. Both results confirmed the hypothesis of a higher protein turnover rates in CEN.PK 113-7D, which was generated in a previous comparative systems biology study of these two yeast strains. The ATP costs associated with the observed differences in protein turnover were quantified and could explain accurately the differences in biomass yield between both strains that are observed in chemostat cultures. The percent of maintenance ATP associated to protein polymerization (polymerization for growth and re-polymerization due to turnover) and degradation was estimated to be 72% for YSBN2 and 79% for CEN.PK 113-7D, which makes these processes the dominant non-biosynthetic drain of ATP in living cells, and hence it represents an energetic parameter of great relevance.