The Abort Code

Okay, so you've activated the self destruct sequence, either by pushing the extrinsic TNF button or by venting cytochrome c from your warp nacelles, and your caspase bomb is counting down to doom. But what if the Klingons back off? What if you figure out at the last minute that the Andromeda strain won't make anybody sick now? What if the Alien falls in the garbage disposal? You need a way to shut down the self-destruct sequence.

Recall that in C. Elegans, there's a gene called ced-9 that suppresses apoptosis. So it is in the mammalian brain, where genes belonging to the Bcl-2 family encode proteins that counteract the processes we've been talking about.

However, mammals, even Giuliani, are somewhat more complex than worms, and so it's not as simple as that. As it turns out, Bcl-2 family genes code for all kinds of proteins--those that suppress apoptosis…and those that promote apoptosis. 

Bcl-2 - family proteins mix and match a variety of protein domains, as shown in the table below. The table also shows which guys where white hats and which wear black hats. There's an easy way to remember it without memorizing the table. In general, if the name of the protein sounds like Bcl ("beck-ul"), then it's anti-apoptotic and wears a white hat. If it doesn't, it's a pro-apoptotic bad guy and wears a black hat. (The exceptions are Bcl-Xs, a bad guy, and A-1, a good guy, but you won't hear too much about them.)








Bcl-2, Bcl-XL, Mcl-1

A1, Bfl-1


Bax, Bak






Bik, Bim




Bad, Bid, Egl-1





Table: The Bcl-2 family proteins, their structure, and their gang affiliation.