Fig. 5

Phosphopeptide enrichment identifies different protein phosphorylation profiles in slow and fast muscle fiber types. a Overview of the experimental setup for phosphopeptide enrichment. Approx. 1000 fibers from separated soleus muscles (n = 5) were screened via the ProFiT assay. Fibers were pooled according to their phenotype and distributed to three technical replicates per fiber type. Phosphopeptide enrichment of soleus type I and IIa fibers was performed using titanium dioxide beads (TiO₂). b Volcano plot comparing phosphopeptide fold-changes between type I and type IIa fibers from the soleus. Colored circles indicate significantly regulated phosphorylation sites (abs. log₂ fold-change > 0.58 and q value < 0.05). c–e Selected protein LFQ intensities (upper panel) and normalized phosphopeptide intensities (lower panel) for significantly different phosphorylation sites on actinin-2 (ACTN2), myosin light chain 1 (MYL1), and obscurin (OBSCN). f Map of titin phosphopeptides. The color code indicates non-regulated and significantly regulated phosphorylation sites (abs. log₂ fold-change > 0.58 and q value < 0.05)