The primary function of rhodopsin kinase is to phosphorylate activated rhodopsin. Once rhodopsin absorbs light, it undergoes a conformational change to become metarhodopsin II. Rhodopsin kinase then adds phosphate groups to the activated rhodopsin, initiating a process that leads to the binding of arrestin. This binding effectively quenches the activity of rhodopsin, preventing further activation of the G-protein transducin and allowing the photoreceptor cell to return to its dark state.
