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Sergey A. Vishnivetskiy, Miyeon Kim, Susan M. Hanson, Xiufeng Song, Whitney M. Cleghorn, Wayne L. Hubbell, Vsevolod V. Gurevich; Robust Self-association Of Arrestin-1 Is Conserved Among Mammalian Species. Invest. Ophthalmol. Vis. Sci. 2011;52(14):52.
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To compare self-association of bovine, mouse, and human arrestin-1
We used multi-angle light scattering to determine self-association constants of wild type and mutant forms of mammalian arrestin-1
Arrestin-1 binds light-activated phosphorhodopsin and ensures rapid signal termination. Its deficiency in humans and mice results in prolonged signaling and rod degeneration. However, most of the biochemical studies were performed on bovine arrestin-1, which was shown to self-associate forming dimers and tetramers, although only the monomer binds rhodopsin. To test whether self-association is a property of arrestin-1 in all mammals we compared self-association parameters of purified human and mouse arrestin-1 with those of bovine counterpart. Mouse and human arrestin-1 also robustly self-associate, existing in monomer-dimer-tetramer equilibrium. Interestingly, the combination of dimerization and tetramerization constants in these three species is strikingly different. While tetramerization of bovine arrestin-1 is highly cooperative, with KD,dim > KD,tet, in mouse KD,dim ~ KD,tet, whereas in human KD,dim << KD,tet. Despite these differences, the shape of the tetramer is likely similar, as homologous mutations effectively prevent self-association of mouse and bovine arrestin-1.
In all three species at very high physiological concentrations of arrestin-1 in rod photoreceptors, most of it is predicted to exist in oligomeric form, with relatively low concentration of free monomer. Due to the differences in self-association constants, the fraction of arrestin-1 that exists as a monomer is the highest in mice, intermediate in cows, and the lowest in humans, inversely correlating with the longevity of these species.
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