The histidin-loop is essential for transport activity of human MDR3. A novel mutation of MDR3 in a patient with progressive familial intrahepatic cholestasis type 3

► A new disease-causing mutation of the phospholipid transporter MDR3 is reported. ► This is the first mutation of the histidine-loop identified in a human ABC transporter. ► The findings approve the importance of the histidine-loop of ABC transporter. ► Ursodeoxycholic acid is an appropriate treatment for this particular mutation of MDR3.