Yet this slight change was enough to radically disrupt the function of patients' lungs, sweat glands, and pancreas. It appears to work like a two-way pump, channeling vital compounds in and out of a cell . When it functions normally, the protein helps regulate the transfer of sodium across cell membranes and serves as a chloride channel. But in CF this process fails, and the chloride channel stays closed. The sodium, which does not move freely, builds up in the lungs and disables a natural antibiotic that would otherwise guard against a wide range of lung infections.
Bacteria then thrive in the thick, sticky mucus.
Two teams of researchers actually did correct the CF defect in a dish by inserting normal genes into cells from CF patients. But treating patients proved more difficult.