Additional file 5 of High-throughput proteomics fiber typing (ProFiT) for comprehensive characterization of single skeletal muscle fibers

Additional file 5 : Suppl. Figure 5: In-vivo SILAC reveals similar Lys-6 labeling after 14 days of MYH isoforms and muscle groups. A) Lys-6 labeling of type I muscle fibers from the soleus ranged from 10% to 80%, with the majority of proteins exhibiting 30–-40% Lys-6 labeling. Notably, albumin (ALB) and transferrin (TF) exhibited ~70% Lys-6 labeling; representative SILAC pairs for the albumin peptide TPVSEHVTK substantiated this high Lys-6 labeling. Grey circles indicate the Lys-0 peptide; red circles the Lys-6-labeled peptide. B) On average, liver proteins exhibited higher Lys-6 labeling rates ranging from ~60–85%. Albumin and transferrin had the same Lys-6 labeling rates in liver tissues as in muscle fibers, suggesting that albumin and transferrin are taken up by muscle fibers via the blood system. The same albumin peptide (TPVSEHVTK) showed similar Lys-6 labeling in muscle fibers and liver tissues. C) Selected SILAC pairs of muscle fiber proteins. The grey circle marks a non-labeled “light” Lys-0 peptide and the red circle illustrates the newly synthesized “heavy” Lys-6 peptide. Titin exhibited very similar Lys-6 incorporation rates in type I and IIa fibers (~31%), whereas Myomesin 2 had a lower incorporation rate in type I fibers (~38%) than type IIa fibers ( ~46%). Conversely, isocitrate-dehydrogenase 3b showed a higher Lys-6 labeling rate in type I ( ~54%) than type IIa fibers ( ~44%).