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Unformatted text preview: family (antiapoptotic family members)—like Bcl-2 itself—
function as inhibitors of apoptosis and programmed cell death. Other members of the Bcl-2 family, however, are proapoptotic proteins that act to
induce caspase activation and promote cell death. There are two groups of
these proapoptotic proteins, which differ in function as well as in their
extent of homology to Bcl-2. Bcl-2 and the other antiapoptotic family members share four conserved regions called Bcl-2 homology (BH) domains.
One group of proapoptotic family members called the “multidomain”
proapoptotic proteins have 3 BH domains (BH1, BH2, and BH3), whereas
the second group, the “BH3-only” proteins, have only the BH3 domain.
The fate of the cell—life or death—is determined by the balance of activity of proapoptotic and antiapoptotic Bcl-2 family members, which act to
regulate one another (Figure 17.7). The multidomain proapoptotic family
members, such as Bax and Bak, are the downstream effectors that directly
induce apoptosis. They...
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