Now, in the absence of this catalytic A chain, this galphaprotein showed a red in the GTP phase, actually has a built in timer. And so it has Gtpa's activity. And that means it can itself turn itself off by using a water molecule to hydrolyze the GTP back into GDP. And remember, when the G protein is in its GDP phase, it is in fact turned off. But what happens here is this catalytic A chain moves on and binds onto this g protein in the GTP phase and it catalyzes a covalent modification process. It basically covalently attaches an ADP ribose component onto this G protein in the GTP phase.