Human UDP-glucuronosyltransferase 1A (UGT1A) isoforms are endoplas-mic reticulum (ER)-resident type I membrane proteins responsible for the detoxification of a broad range of toxic phenolic compounds. These pro-teins contain a C-terminal stop transfer sequence with a transmembrane domain (TMD), which anchors the protein into the membrane, followed by a short cytosolic tail (CT).