Gating differences occur between the α-subunits of the bovine and rat clones of an amiloride-sensitive epithelial Na+ channel (ENaC). Deletion of the carboxy terminus of bovine α-ENaC (α-bENaC) at R567 converted the gating properties to that of rat α-ENaC (α-rENaC). The equivalent truncation in α-rENaC was without effect on the gating of the rat homologue. The addition of actin to ENaC channels composed of either α-rENaC or α-bENaC alone produced a two fold reduction in conductance and an increase in open probability. Neither α-rENaC (R613X) nor α-bENaC (R567X) was responsive to actin. Using a chimera consisting of αrENaC1-615 and α-bENaC570-650, we examined several different carboxy-terminal truncation mutants plus and minus actin. When incorporated into planar bilayers, the gating pattern of this construct was identical to wild-type (wt) α-bENaC. Premature stop mutations proximal to E685X produced channels with gating patterns like α-rENaC. Actin had no effect on the E631X truncation, whereas more distal truncations all interacted with actin, as did wt α-bENaC. Key findings were confirmed using channels expressed in Xenopus oocytes and studied by cell-attached patch-clamp recording. Our results suggest that the site of actin regulation at the carboxy terminus of the chimera is located between residues 631 and 644.