Abstract
Presenilin is an integral membrane aspartate protease that regulates cellular processes by cleaving proteins within the cell membrane. The recent crystal structure of presenilin reveals a conspicuous pore in a bundle of nine α-helices, which was originally thought to adopt a novel protein fold. However, here I show that the presenilin fold is a variant of the ClC chloride channel/transporter fold. This observation may have important implications for presenilin's postulated biological role as a calcium leak channel.
