Structure and function of the visual arrestin oligomer

• DOI: 10.1038/sj.emboj.7601614
• Publication Date: 2007-03-02T01:46:21Z
• Authors: Susan M Hanson; Ned Van Eps; Derek J Francis; Christian Altenbach; Sergey A Vishnive...; Vadim Y Arshavsky; Candice S Klug; Wayne L Hubbell; Vsevolod V Gurevich
• Keywords: Models, Molecular; 0301 basic medicine; Rhodopsin; 0303 health sciences; Arrestin; Magnetic Resonance Spectroscopy; Light; Microtubules; 03 medical and health sciences; Oligodeoxyribonucleotides; Mutagenesis, Site-Directed; Animals; Humans; Scattering, Radiation; Cattle; Phosphorylation; Crystallization; Protein Binding

A distinguishing feature of rod arrestin is its ability to form oligomers at physiological concentrations. Using visible light scattering, we show that rod arrestin forms tetramers in a cooperative manner in solution. To investigate the structure of the tetramer, a nitroxide side chain (R1) was introduced at 18 different positions. The effects of R1 on oligomer formation, EPR spectra, and inter-spin distance measurements all show that the structures of the solution and crystal tetramers are different. Inter-subunit distance measurements revealed that only arrestin monomer binds to light-activated phosphorhodopsin, whereas both monomer and tetramer bind microtubules, which may serve as a default arrestin partner in dark-adapted photoreceptors. Thus, the tetramer likely serves as a 'storage' form of arrestin, increasing the arrestin-binding capacity of microtubules while readily dissociating to supply active monomer when it is needed to quench rhodopsin signaling.