FIG. 3.
Analysis of phosphorylated peptides (pp0, pp1, and pp2) derived from radiolabeled β4 integrin. 32P radiolabeled peptides were eluted from TLE or TLC plates and subjected to phosphoamino acid analysis (A) or Edman degradation (B and C). The peptides were degraded for at least 2 cycles. Notice that the phosphate is shed during the first cycle for pp0, pp1, and pp2 (B). In contrast, ppf (C), used as a control, did not shed any phosphate (PO4 position) during the first 2 cycles. ori, sample origin; +, anode; −, cathode; S, phosphoserine; T, phosphothreonine; Y, phosphotyrosine.