Fig. 6
From: Freeze-dried plasma proteins are stable at room temperature for at least 1 year
The location of the most common peptide sequences that were cleaved within the complement C4B protein from the protein accession NP_001002029.3 The peptide sequence NGFKSHALQLNNRQIR shows no significant relationship to any other protein and contained 31% of all observed peptides from C4B. The peptide sequence GLEEELQFSLGSKINVK accounted for 11% of all peptides. The arrows show the locations of the main peptide cleavage sites on the carboxyl side of the isoprene C2 domain at a site within a sequence of basic, acid and polar amino acids. The bracket shows a section of the preproprotein that is also cleaved upon warming to room temperature producing the mature chain detectable by Western blot. The C4B amino acid sequence 1337RNGFKSHALQLNNRQIRGLEEELQFSLGSKINVK1370 on the carboxyl side of the isoprene C2-like superfamily domain was the most frequent site of cleavage (see arrows). The sub-sequence 1137NGFKSHALQLNNR1352 is located just to the carboxyl terminal side of a local hydrophilic maximum and flanks the evolutionarily conserved isoprene C2 sequence shared by the innate defense proteins complement 4A/B and alpha 2 macroglobulin. The cleavage sites of the peptide(s) NGFKSHALQLNNRQIR are flanked on the amino side by short stretches of hydrophilic amino acids, the released peptide includes asparagine and glutamine, and there is a stretch of three glutamic acid residues and glutamine adjacent on the carboxyl side of the cleavage site