title: Opposing effects of inositol hexakisphosphate on rod arrestin and arrestin2 self-association.
abstract: The robust cooperative formation of rod arrestin tetramers has been well-established, whereas the ability of other members of the arrestin family to self-associate remains controversial. Here, we used purified arrestins and multi-angle light scattering to quantitatively compare the propensity of the four mammalian arrestin subtypes to self-associate. Both non-visual and cone arrestins only form oligomers at very high non-physiological concentrations. However, inositol hexakisphosphate (IP6), a fairly abundant form of inositol in the cytoplasm, greatly facilitates self-association of arrestin2. Arrestin2 self-association equilibrium constants in the presence of 100 microM IP6 suggest that an appreciable proportion could exist in an oligomeric state but only in intracellular compartments where its concentration is 5-10-fold higher than average. In contrast to arrestin2, IP6 inhibits self-association of rod arrestin, indicating that the structure of these two tetramers in solution is likely different.
authors.affiliation: Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Hanson
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Vishnivetskiy
authors.forename: Wayne L
authors.initials: WL
authors.lastname: Hubbell
authors.forename: Vsevolod V
authors.initials: VV
authors.lastname: Gurevich
mesh_terms: D000818:Animals; D019393:Arrestin / Q000737:chemistry* / Q000378:metabolism; D019390:Arrestins / Q000737:chemistry* / Q000378:metabolism; D002417:Cattle; D002850:Chromatography, Gel; D019281:Dimerization; D006801:Humans; D007834:Lasers; D008027:Light; D008970:Molecular Weight; D010833:Phytic Acid / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012542:Scattering, Radiation; D000071557:beta-Arrestins
chemical_list: D019393:Arrestin; D019390:Arrestins; D011994:Recombinant Proteins; C082333:arrestin3; D000071557:beta-Arrestins; D010833:Phytic Acid