Affinity of rhodopsin to raft enables the aligned oligomer formation from dimers: Coarse-grained molecular dynamics simulation of disk membranes

PLoS One. 2020 Feb 7;15(2):e0226123. doi: 10.1371/journal.pone.0226123. eCollection 2020.

Abstract

The visual photopigment protein rhodopsin (Rh) is a typical G protein-coupled receptor (GPCR) that initiates the phototransduction cascade in retinal disk membrane of rod-photoreceptor cells. Rh molecule has a tendency to form dimer, and the dimer tends to form rows, which is suggested to heighten phototransduction efficiency in single-photon regime. In addition, the dimerization confers Rh an affinity for lipid raft, i.e. raftophilicity. However, the mechanism by which Rh-dimer raftophilicity contributes to the organization of the higher order structure remains unknown. In this study, we performed coarse-grained molecular dynamics simulations of a disk membrane model containing unsaturated lipids, saturated lipids with cholesterol, and Rh-dimers. We described the Rh-dimers by two-dimensional particle populations where the palmitoyl moieties of each Rh exhibits raftophilicity. We simulated the structuring of Rh in a disk for two types of Rh-dimer, i.e., the most and second most stable Rh dimers, which exposes the raftophilic regions at the dimerization-interface (H1/H8 dimer) and two edges away from the interface (H4/H5 dimer), respectively. Our simulations revealed that only the H1/H8 dimer could form a row structure. A small number of raftophilic lipids recruited to and intercalated in a narrow space between H1/H8 dimers stabilize the side-by-side interaction between dimers in a row. Our results implicate that the nano-sized lipid raft domains act as a "glue" to organize the long row structures of Rh-dimers.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cholesterol / metabolism
  • Crystallography, X-Ray
  • Fatty Acids, Unsaturated / metabolism
  • Kinetics
  • Lipid Bilayers / metabolism
  • Lipoylation
  • Membrane Microdomains / metabolism
  • Membranes / chemistry
  • Membranes / metabolism
  • Models, Molecular
  • Molecular Dynamics Simulation*
  • Protein Conformation, alpha-Helical
  • Protein Multimerization*
  • Retinal Rod Photoreceptor Cells / metabolism
  • Rhodopsin / chemistry*
  • Rhodopsin / metabolism*

Substances

  • Fatty Acids, Unsaturated
  • Lipid Bilayers
  • Rhodopsin
  • Cholesterol

Grants and funding

This work was supported by: A.A., JSPS KAKENHI Grant Number 17K05614, https://www.jsps.go.jp/english/index.html, No; A.A., Japan-Korea Basic Scientific Cooperation Program, https://www.jsps.go.jp/english/index.html, No; K.M., JSPS KAKENHI Grant Number 17KT0024, https://www.jsps.go.jp/english/index.html, No.