PUMA BH3 is a p53 upregulated modulator of apoptosis (PUMA) BH3 domain peptide that acts as a direct activator of Bak with a Kd of 26 nM. This peptide binds Bcl-2, localizes to mitochondria, and induces cytochrome C release.
This peptide, generated from the BH3 domain of Bak (Flu-BakBH3), has been shown to have high-affinity binding to a surface pocket of the Bcl-XL protein that is required for its death antagonist function.