BID is a pro-apoptotic member of the 'BH3-only' (BOPS) subset of the BCL-2 family of proteins that constitute a critical control point in apoptosis. Bid is the first of the BOPs reported to bind and activate Bcl-2, Bax, and Bak. Bid serves as a death-inducing ligand that moves from the cytosol to the mitochondrial membrane to inactivate Bcl-2 or to activate Bax.
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.