Incorporation of a Retinal Rod cGMP-Dependent Conductance into Planar Bilayers

The light-modulated current of vertebrate retinal rods flows through a 3′,5′-cyclic GMP-dependent conductance located in the outer segment plasma membrane. We report the incorporation into planar bilayers of a conductance derived from vertebrate rod outer segment membranes specifically activated by cGMP but not by cAMP, 5′-GMP, GTP, or 5′-AMP. When the mean currents were measured as a function of increasing cGMP concentration, maximal activation occurred at concentrations