FIGURE 2.

MS/MS and C-terminal amino acid sequence analysis. The prominent fragment of the hFibrinogen α chain that formed after this plasma protein was incubated with a recombinant hTryptase-β·heparin complex for 15 min (75:1 enzyme:substrate ratio) was purified by SDS-PAGE and then subjected to C-terminal amino acid sequence analysis by LC-MS/MS. Shown are the susceptible peptides that were identified in the analyses. The entire fragment was mapped. The 19-mer sequence highlighted in pink corresponds to the protein N-terminal signal peptide of the protein that was not present in the analyzed protein as it is removed in the endoplasmic reticulum before the protein is secreted from its expressing cell. The vertical red line highlights Lys⁵⁷⁵, which is the preferred site of cleavage by the hTryptase-β·heparin complex.