 Defects in GRK1 result in Oguchi stationary night blindness.GRK7 similarly regulates cone opsin phosphorylation and deactivation in color vision, together with cone arrestin, also known as arrestin-4 or X-arrestin.GRK2 was first identified as an enzyme that phosphorylated the beta-2 adrenergic receptor, and was originally called the beta adrenergic receptor kinase (βARK, or ββARK1).