A transporter is a transmembrane protein that binds to substances inside or outside the cell, ingesting or pumping these substances out of the cell. It is mainly distributed on the surface of cells such as the intestine, liver, kidney, and brain. Transporter proteins only participate in the transportation of substances and do not alter their chemical structure. The changes in drug transport characteristics caused by transporters are important factors in causing clinical drug interactions, and are an important component of the study of new drug formation in vitro interactions.