This is 22 amino acids flagellin peptide known as flg2. It spans the core domain necessary for binding and biological activity in plant cells. This peptide spanning the 22 amino acids in the core of the conserved domain induces responses after treatment with fungal elicitors such as chitin fragments, xylanase, ergosterol, and high-mannose–type glycopeptides when applied in subnanomolar concentrations. Flagellin is the structural protein that forms the major portion of flagellar filaments. Flagellins from different bacterial species vary in their central part but show conservation of their N-terminal and C-terminal regions.
Pyroglutamyl (pGlu) peptides may spontaneously form when either Glutamine (Q) or Glutamic acid (E) is located at the sequence N-terminus. The conversion of Q or E to pGlu is a natural occurrence and in general it is believed that the hydrophobic γ-lactam ring of pGlu may play a role in peptide stability against gastrointestinal proteases. Pyroglutamyl peptides are therefore considered a normal subset of such peptides and are included as part of the peptide purity during HPLC analysis.