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This is the overall Dimer. The membrane access channel is accessible to lipids partitioned in the inner layer of the lipid bilayer. This is the Membrane Access Channel (MAC). This is the Acyl Chain Binding Pocket (ABP) and Cytosolic Port (CP).

The surface of FAAH reveals two equivalent openings (Opening 1, Opening 2) directly accessible by the inner layer of the lipid bilayer.^[1] These Membrane Access Channels (MAC) are made up of three flaps and two intrusions which collectively form the entry way for the aliphatic binding of the amide lipid substrate. Flaps 1 and 2 envelope the middle and backside of the anandamide mimic, and are locked together by a salt bridge between Arg486 and Asp403. Flap 2 contains a very hydrophobic membrane binding cap that partially covers the opening with Phe432. This binding cap clings to the cell's hydrophobic inner membrane and uses a multitude of positively charged residues to lure out partitioned anandamide by its narrow partial negative charge. The catalytic site is defined by the catalytic triad: the 238-241 anionic hole loop contributes the nucleophilic S241, loop 3 contributes the neighboring S217 upon forming the very top of the membrane access channel, and a fourth loop contributes the K142.

The membrane access channel leads to the active site, which is flanked by both the acyl chain binding pocket and cytosolic port (ABP and CP).^[2] The cytosolic port is a lengthy, flexible loop that leads directly into the cytoplasm, allowing the deacylated amine to enter the cell.