It is a glycoprotein with 12 membrane spanning domains. It is seen in epithelia in various parts of the body and is involved in both absorptive and secretory activities.
There are distinct isoforms for secretory and absorptive function. The absorptive form is found exclusively in thick segment of ascending limb of loop of henle.
Frusemide binds to the Cl- binding site of Na+ K+ 2Cl- Co-transporter and blocks it, thus causing diuresis.
The secretory form is found in the basolateral membrane of most glandular and epithelial cells.