PUMA BH3 is a sequence derived from the BH3 domain of the BH3-only protein PUMA (p53 up-regulated modulator of apoptosis]. PUMA, also known as Bcl-2-binding component 3 (BBC3), is a pro-apoptotic protein and member of the Bcl-2 protein family. Bcl-2 family proteins regulate the mitochondrial apoptosis pathway by controlling mitochondrial outer membrane permeabilization. The BCL2 protein family is divided into three subfamilies: antiapoptotic BCL2 family proteins, including BCL2, BCLxL, and MCL1, proapoptotic multi-domain BCL2 family proteins, including BAK, BAX, and BOK, and proapoptotic BH3-only proteins, including BIM, PUMA, BID, BAD, NOXA, BMF, HRK, and BIK. PUMA acts as a key mediator of cytosolic proapoptotic p53 function by freeing cytosolic p53 from inactive complexes with BCL-xL
