Conformational change opening the CFTR chloride channel pore coupled to ATP-dependent gating

► Opening of the CFTR channel pore is controlled by ATP binding and hydrolysis. ► The conformational changes in the pore triggered by ATP are not known. ► We have used site-specific modification to identify changes in pore conformation. ► Pharmacological or mutagenic interference with ATP hydrolysis alters modification. ► Our results identify the location of a gate within the pore that is opened by ATP.