PT  - JOURNAL ARTICLE
AU  - George Khelashvili
AU  - Anoop Narayana Pillai
AU  - Joon Lee
AU  - Kalpana Pandey
AU  - Alexander M. Payne
AU  - Zarek Siegel
AU  - Michel A. Cuendet
AU  - Tylor R. Lewis
AU  - Vadim Y. Arshavsky
AU  - Johannes Broichhagen
AU  - Joshua Levitz
AU  - Anant K. Menon
TI  - Unusual mode of dimerization of retinitis pigmentosa-associated F220C rhodopsin
AID  - 10.1101/2020.12.28.424580
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.12.28.424580
4099  - http://biorxiv.org/content/early/2020/12/29/2020.12.28.424580.short
4100  - http://biorxiv.org/content/early/2020/12/29/2020.12.28.424580.full
AB  - Mutations in the G protein-coupled receptor (GPCR) rhodopsin are a common cause of autosomal dominant retinitis pigmentosa, a blinding disease. Rhodopsin self-associates in the membrane, and the purified monomeric apo-protein opsin dimerizes in vitro as it transitions from detergent micelles to reconstitute into a lipid bilayer. We previously reported that the retinitis pigmentosa-linked F220C opsin mutant fails to dimerize in vitro, reconstituting as a monomer. Using fluorescence-based assays and molecular dynamics simulations we now report that whereas wildtype and F220C opsin display distinct dimerization propensities in vitro as previously shown, they both dimerize in the plasma membrane of HEK293 cells. Unexpectedly, molecular dynamics simulations show that F220C opsin forms an energetically favored dimer in the membrane when compared with the wild-type protein. The conformation of the F220C dimer is unique, with transmembrane helices 5 and 6 splayed apart, promoting widening of the intracellular vestibule of each protomer and influx of water into the protein interior. FRET experiments with SNAP-tagged wild-type and F220C opsin expressed in HEK293 cells are consistent with this conformational difference. We speculate that the unusual mode of dimerization of F220C opsin in the membrane may have physiological consequences.