X-ray crystal structure of arrestin from bovine rod outer segments.

Retinal arrestin is the essential protein for the termination of the light response in vertebrate rod outer segments. It plays an important role in quenching the light-induced enzyme cascade by its ability to bind to phosphorylated light-activated rhodopsin (P-Rh*). Arrestins are found in various G-protein-coupled amplification cascades.

Crystallization and preliminary X-ray analysis of arrestin from bovine rod outer segment.

We present the first X-ray study of a member of the arrestin family, the bovine retinal arrestin. Arrestin is essential for the fine regulation and termination of the light-induced enzyme cascade in vertebrate rod outer segments. It plays an important role in quenching phototransduction by its ability to preferentially bind to phosphorylated light-activated rhodopsin.

Duration and amplitude of the light-induced cGMP hydrolysis in vertebrate photoreceptors are regulated by multiple phosphorylation of rhodopsin and by arrestin binding.

The duration and amplitude of the light-induced cGMP hydrolysis in bovine rod outer segments were investigated using purified rhodopsin in nine different states of phosphorylation in a reconstituted system. Effects of varying amounts of arrestin at all states of rhodopsin phosphorylation were measured. The findings were the following: (1) At low bleaching levels, the activity of phosphodigesterase (PDE) depends strongly on the phosphorylation degree of the light-activated rhodopsin (R*), while at saturating light levels R* of all phosphorylation degrees activates PDE to the same extent.

Deactivation of photoactivated rhodopsin by rhodopsin-kinase and arrestin.

Photoactivated rhodopsin (R) catalyses, by repetitively interacting with many copies of a guanosine nucleotide binding protein (transducin), the amplified binding of GTP to transducin molecules which then activate cyclic GMP phosphodiesterase. Electrophysiologists recently have shown that cyclic GMP keeps ion channels in the plasma membrane of the rod outer segment open in darkness, and that light-induced hydrolysis of cyclic GMP leads to closure of the channels and therefore to hyperpolarization of the rod cell. Photoactivated rhodopsin interacts not only with transducin, but with two more proteins: a protein kinase that specifically phosphorylates R (in contrast to dark-adapted rhodopsin) at multiple sites; and an abundant soluble protein of 48 KDal (called 48 K-protein, S-antigen, or arrestin) that specifically binds to phosphorylated R.

Rapid affinity purification of retinal arrestin (48 kDa protein) via its light-dependent binding to phosphorylated rhodopsin.

Arrestin (also named '48 kDa protein' or 'S-antigen') is a soluble protein involved in controlling light-dependent cGMP phosphodiesterase activity in retinal rods, and is also known for its ability to induce autoimmune uveitis of the eye. We report a rapid and simple purification method based on the property of arrestin to bind specifically and reversibly to illuminated and phosphorylated rhodopsin [(1984) FEBS Lett. 176, 473-478].