Abstract
Abstract: :
Arrestin binds tightly to phosphorylated light–activated rhodopsin and prevents its further interaction with transducin, thereby quenching light–induced signaling. Serious visual disorders are linked to mutations in arrestin, suggesting that arrestins play a key role in the mechanism of desensitization of rod and cone photoreceptors. Mammals express four arrestin proteins, two visual arrestins (expressed in the rod and cone photoreceptor cells of the retina) and non–visual arrestin 2 and 3 (also called ß–arrestin 1 and 2). Previously we have cloned the genes encoding the rod and cone arrestins from the retina of the tiger salamander (Ambystoma tigrinum). Their identity was established by virtue of their selective expression in rods and cones, respectively. Cones are less sensitive than rods to dim light, but demonstrate faster kinetics of signaling and desensitization. To analyze the structural basis of desensitization of cone photoreceptors, we crystallized cone arrestin from salamander. Crystals were obtained by sitting drop vapor diffusion technique and belong to space group P212121 (a=70.36, b=75.64, c=78.84). There is one molecule per asymmetric unit and the resolution is 2.3Å. Details of the analysis will be presented. This work was supported by NIH grants EY11500 and GM63097 (VVG), and EY014218, GM416130 and Welch Foundation to JN, and The Burroughs–Wellcome Fund support to BS.
Keywords: photoreceptors • computational modeling • protein structure/function