Figure 1.

Discovery of new members of the long-lived proteome. (A) Pulse-chase labeling of whole rats. Depicted is a schematic of the pulse-chase labeling procedure. Litters of rats were fully ¹⁵N-labeled through feeding a ¹⁵N diet starting from a previous generation. Fully labeled rats were then switched to a normal ¹⁴N diet (chase) at 6 weeks post-natal, and sacrificed a 0, 4, 6, 9, and 12 months post-chase. Tissues were harvested, fractionated, and analyzed by MS (B) Tissue localization of long-lived proteins. ¹⁵N spectral counts were calculated and plotted as a percentage of total spectral counts in each fraction of liver (grey) and brain (black) tissues from an animal 6-months post-chase. (C) Cellular localization and processes of long-lived proteins. Identified long-lived proteins were sorted by subcellular localization (upper) and cellular process (lower), and plotted as a pie chart, inset numbers representing the number of proteins per localization. (D-G) MS1 traces of representative peptides. Aligned elution profile MS1 traces are plotted for representative peptides for alpha collagen VI (D), myelin proteolipid protein (E), Sirt2 (F), and Enpp6 (G), with ¹⁵N signal in orange and ¹⁴N signal in grey. See also Figure S1-3.