Singlet oxygen modification abolishes voltage-dependent inactivation of the sea urchin spHCN channel.

Photochemically or metabolically generated singlet oxygen (1 O2 ) reacts broadly with macromolecules in the cell. Because of its short lifetime and working distance, 1 O2 holds potential as an effective and precise nanoscale tool for basic research and clinical practice. Here we investigate the modification of the spHCN channel that results from photochemically and chemically generated 1 O2 The spHCN channel shows strong voltage-dependent inactivation in the absence of cAMP. In the presence of photosensitizers, short laser pulses transform the gating properties of spHCN by abolishing inactivation and increasing the macroscopic current amplitude. Alanine replacement of a histidine residue near the activation gate within the channel's pore abolishes key modification effects. Application of a variety of chemicals including 1 O2 scavengers and 1 O2 generators supports the involvement of 1 O2 and excludes other reactive oxygen species. This study provides new understanding about the photodynamic modification of ion channels by 1 O2 at the molecular level.