Obtaining a reliable 3D model for the complex formed by photoactivated rhodopsin (R*) and its G-protein, transducin (Gtalphabetagamma), would significantly benefit the entire field of structural biology of G-protein-coupled receptors (GPCRs). In this study, we have performed extensive configurational sampling for the isolated C-terminal fragment of the alpha-subunit of transducin, Gtalpha 340-3...

Rhodopsin is a seven-transmembrane helix receptor that binds and catalytically activates the heterotrimeric G protein transducin (G(t)). This interaction involves the cytoplasmic surface of rhodopsin, which comprises four putative loops and the carboxyl-terminal tail. The fourth loop connects the carboxyl end of transmembrane helix 7 with Cys(322) and Cys(323), which are both modified by membra...

Visual signal transduction is initiated by the photoisomerization of 11-cis retinal upon rhodopsin ligation. Unlike vertebrate rhodopsin, which interacts with Gt-type G-protein to stimulate the cyclic GMP signaling pathway, invertebrate rhodopsin interacts with Gq-type G-protein to stimulate a signaling pathway that is based on inositol 1,4,5-triphosphate. Since the inositol 1,4,5-triphosphate ...

The rhodopsin crystal structure provides a structural basis for understanding the function of this and other G protein-coupled receptors (GPCRs). The major structural motifs observed for rhodopsin are expected to carry over to other GPCRs, and the mechanism of transformation of the receptor from inactive to active forms is thus likely conserved. Moreover, the high expression level of rhodopsin ...

Retinitis pigmentosa (RP) is a clinically and genetically heterogeneous degenerative eye disease. Mutations at Arg135 of rhodopsin are associated with a severe form of autosomal dominant RP. This report presents evidence that Arg135 mutant rhodopsins (e.g., R135L, R135G, and R135W) are hyperphosphorylated and bind with high affinity to visual arrestin. Mutant rhodopsin recruits the cytosolic ar...

Precise vectorial transport of rhodopsin is essential for rod photoreceptor health and function. Mutations that truncate or extend the C terminus of rhodopsin disrupt this transport, and lead to retinal degeneration and blindness in human patients and in mouse models. Here we show that such mutations disrupt the binding of rhodopsin to the small GTPase rab11a. The rhodopsin-rab11a interaction i...

PURPOSE The purpose of our study was to determine whether arrestin residues previously predicted by computational modeling to interact with an aspartic acid substituted rhodopsin tail are actually involved in interactions with phospho-residues on the rhodopsin cytoplasmic tail. METHODS We generated arrestin mutants with altered charges at predicted positions. These mutants were then tested fo...

Opsin, the rhodopsin apoprotein, was recently shown to be an ATP-independent flippase (or scramblase) that equilibrates phospholipids across photoreceptor disc membranes in mammalian retina, a process required for disc homoeostasis. Here we show that scrambling is a constitutive activity of rhodopsin, distinct from its light-sensing function. Upon reconstitution into vesicles, discrete conforma...

BACKGROUND The retinal rod outer segment is a sensory cilium that is specialized for the conversion of light into an electrical signal. Within the cilium, up to several thousand membranous disks contain as many as a billion copies of rhodopsin for efficient photon capture. Disks are continually turned over, requiring the daily synthesis of a prodigious amount of rhodopsin. To promote axial diff...

PURPOSE Salamander photoreceptor cells have been used widely as models in vision research. However, the salamander opsin genes had not been cloned. The purpose of this study was to clone a salamander rhodopsin and to determine its primary structure and cell type-specific expression. METHODS Using salamander retina RNA as a template and Xenopus rhodopsin-specific oligonucleotides as primers, r...