Fig. 1.

Proteome-wide quantitation of k_degin mammalian fibroblasts.A, phylogenetic tree and maximal life spans of species analyzed in this study. Colors indicate distinct orders and suborders. B, dynamic SILAC experimental design. Blue and red colors indicate unlabeled and isotopically labeled spectra/cells, respectively. C, labeling kinetics of human HSP90B1 (endoplasmin) shown as an example of protein-level determination of k_deg values. Blue dots indicate the fraction labeled for all peptides mapped to the protein, and red dots indicate the median fraction labeled for all peptides. The blue curve is a least squares fit to a first-order exponential equation used to measure the indicated k_deg value. D, pairwise comparison of k_deg measurements in biological replicates of bowhead whale cells. The solid line indicates the identity line. The r value indicates the Pearson correlation coefficient. E, distribution of k_deg measurements for each species. The box plots indicate the median (white line), the interquartile range (box), and complete range (whiskers) of k_deg measurements excluding far outliers (>2 SD). The number in each box indicates the number of protein-level k_deg measurements. Red and blue boxes distinguish data collected in this study and the previous study by Swovick et al. (21), respectively. SILAC, stable isotopic labeling in cell culture.