Speaker
Dr
Achim Stocker
(Uni Bern)
Description
11-cis-retinal is the photon accepting cofactor of rhodopsin in the primary light reaction within rod- and cone receptor cells. Persistent vision affords the enzymatic re-isomerization of accumulating all-trans-retinal to 11-cis-retinal in the retinal pigment epithelium (RPE). Cellular retinaldehyde binding protein (CRALBP) is essential for vision by routing 11-cis-retinoids for the conversion of photobleached opsin molecules into photosensitive rhodopsin pigments.
Here, we report the high-resolution (1.8 Å) crystal structure of the R234W mutant of CRALBP (R234W) in complex with its less abundant isomer 9-cis-retinal, a naturally occurring alternate isomer that is used in retinal replacement therapies. A structural overlay with the known 11-cis:R234W complex reveals alternate binding for the 9-cis-aldehyde tail and a strong deformation of the ligand arround position C11/C12. We have complemented our structural study with single crystal UV/Visible spectroscopy of the 9-cis:R234W complex, as well as spectrally characterizing crystals of the 11-cis:WT and the 11-cis:R234W complexes. The single crystal spectral data has provided detailed information as to the nature of the bound ligand within the crystal through the observation of a dose dependent X-ray induced radical peak at 545nm. The chemical nature of the 9-cis-retinal has been further probed by QM/MM simulation and has allowed us to propose a mechanism for the stabilization of a ground-state radical of retinal within R234W.
Primary author
Dr
Achim Stocker
(Uni Bern)
Co-authors
Dr
Arwen R Pearson
(University of Leeds)
Ms
Christin S Bolze
(University of Bern)
Dr
Florian Dworkowski
(Swiss Light Source)
Dr
Guillaume Pompidor
(Swiss Light Source)
Prof.
Krzysztof Palczewski
(Case Western Reserve University)
Dr
Marcin Golczak
(Case Western Reserve University)
Dr
Martin Fuchs
(Swiss Light Source)
Prof.
Michele Cascella
(University of Bern)
Ms
Rachel Helbling
(University of Bern)
Dr
Robin Owen
(Diamond Light Source)
Mr
Walter Aeschimann
(University of Bern)
Dr
Xiaoqin He
(PSI Villigen)
