The ATP-binding cassette (ABC) transporter family are primary active transporters that use ATP hydrolysis to drive the transport of substrates across the membrane. The ABCB half transporter subfamily must dimerize to form a functional transporter. The Heavy metal tolerance factor 1 (HMT-1) subfamily are vacuolar proteins that function in heavy metal detoxification. They are distinguished from other ABCB half-transporters by the presence of a hydrophobic N-terminal extension. (Adapted from FBrf0207211 and FBrf0224053.)