Characterization of the Simultaneous Decay Kinetics of Metarhodopsin States II and III in Rhodopsin by Solution-State NMR Spectroscopy.
Related Articles Characterization of the Simultaneous Decay Kinetics of Metarhodopsin States II and III in Rhodopsin by Solution-State NMR Spectroscopy.
Angew Chem Int Ed Engl. 2014 Feb 6;
Authors: Stehle J, Silvers R, Werner K, Chatterjee D, Gande S, Scholz F, Dutta A, Wachtveitl J, Klein-Seetharaman J, Schwalbe H
Abstract
The mammalian visual dim-light photoreceptor rhodopsin is considered a prototype G protein-coupled receptor. Here, we characterize the kinetics of its light-activation process. Milligram quantities of ?,?-(15) N-labeled tryptophan rhodopsin were produced in stably transfected HEK293 cells. Assignment of the chemical shifts of the indole signals was achieved by generating the single-point-tryptophan to phenylalanine mutants, and the kinetics of each of the five tryptophan residues were recorded. We find kinetic partitioning in rhodopsin decay, including three half-lives, that reveal two parallel processes subsequent to rhodopsin activation that are related to the photocycle. The meta II and meta III states emerge in parallel with a relative ratio of about 3:1. Transient formation of the meta III state was confirmed by flash photolysis experiments. From analysis of the site-resolved kinetic data we propose the involvement of the E2 -loop in the formation of the meta III state.
PMID: 24505031 [PubMed - as supplied by publisher]
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