Structural role of the T94I rhodopsin mutation in congenital stationary night blindness

Abstract

Congenital stationary night blindness (CSNB) is an inherited and non-progressive retinal dysfunction. Here, we present the crystal structure of CSNB-causing T94I2.61 rhodopsin in the active conformation at 2.3 Å resolution. The introduced hydrophobic side chain prolongs the lifetime of the G protein activating metarhodopsin-II state by establishing a direct van der Waals contact with K296, the site of retinal attachment. This is in stark contrast to the light-activated state of the CSNB-causing G90D2.57 mutation, where the charged mutation forms a salt bridge with K296 7.43. To find the common denominator between these two functional modifications, we combined our structural data with a kinetic biochemical analysis and molecular dynamics simulations. Our results indicate that both the charged G90D2.57 and the hydrophobic T94I 2.61 mutation alter the dark state by weakening the interaction between the Schiff base (SB) and its counterion E113 3.28 . We propose that this interference with the tight regulation of the dim light photoreceptor rhodopsin increases background noise in the visual system and causes the loss of night vision characteristic for CSNB patients.

Crystal structure of rhodopsin in complex with a mini-G o sheds light on the principles of G protein selectivity

“…Rhodopsin is the first GPCR that had structures determined in the inactive and active states with and without agonist ( 9 ) and in an arrestin-bound state ( 5 ). In addition, rhodopsin is the only GPCR for which structures of human disease mutants have been solved ( 10 , 11 ). Comparisons of these structures revealed that rhodopsin activation results in the opening of a cleft on the cytoplasmic side of the receptor and the formation of a binding cavity for the C-terminal domain (α5) of G t .…”

Strategic Screening and Characterization of the Visual GPCR-mini-G Protein Signaling Complex for Successful Crystallization

“…The protocol integrates a set of methods to qualitatively evaluate the impact of detergent and deglycosylation during preparation of the rhodopsin-mini-G o complex. Rhodopsin at inactive state and light-activated state bound with and without the transducin peptide has been crystallized when purified in the detergents octyl glucoside (C8G) 20,21,22 and C9G 23,24 . As the rhodopsin-mini-G o complex purified in C8G and C9G did not yield crystals (data not shown), we then explored a wider range of other detergents using the strategy described (Figure 1).…”

The role of water molecules in phototransduction of retinal proteins and G protein-coupled receptors

“…4-7 were prepared using PYMOL (The PyMOL Molecular Graphics System, Version 2.0 Schrödinger, LLC.) from the coordinates of inactive (PDB ID: 1GZM 17 ) and active (PDB ID: 2X72 32 ) bovine rhodopsin, of the adenosine A2A receptor solved by serial millisecond crystallography at room-temperature (PDB ID: 5NM4 22 ), of the T94I rhodopsin mutant (5DYS 19 ), and of bacteriorhodopsin in the ground state obtained with serial femtosecond crystallography (5J7A 29 ).…”

“…[11][12][13][14][15] These water molecules have several roles including an essential function for the changes that occur aer activation. Specically, three major roles can be assigned to water molecules: (1) they can be important components of hydrogen bond networks that stabilise the overall structures of inactive and active states 11,[16][17][18][19] (Fig. 2 and 3); (2) they can provide a local hydrophilic environment for polar ligands (Fig.…”