Structural and functional analysis of the native peripherin-ROM1 complex isolated from photoreceptor cells

Area of Science:

• Biochemistry
• Structural Biology
• Ophthalmology

Background:

• Peripherin and ROM1 are retina-specific tetraspanins crucial for photoreceptor outer segment structure and function.
• Mutations in peripherin are linked to over 100 inherited retinal dystrophies.
• The native complex structure and function of peripherin-ROM1 have remained poorly understood due to purification challenges.

Purpose of the Study:

• To develop a high-yield purification method for the native peripherin-ROM1 complex.
• To characterize the biochemical and biophysical properties of the peripherin-ROM1 complex.
• To elucidate the structural basis of peripherin-ROM1 function in membrane organization.

Main Methods:

• High-yield purification of peripherin-ROM1 from bovine retinas.
• Size exclusion chromatography and blue native gel electrophoresis to determine complex stoichiometry.
• Liquid chromatography tandem mass spectrometry for glycan analysis.
• Electron microscopy for structural determination.
• Reconstitution into lipid vesicles to assess membrane curvature induction.

Main Results:

• A simplified method yielded high quantities of the native peripherin-ROM1 complex.
• The native complex was confirmed to be a stable tetramer.
• Peripherin is glycosylated, while ROM1's glycosylation site and composition were characterized.
• Electron microscopy provided an 18 Å resolution structure of the tetramer, revealing an elongated shape with 2-fold symmetry.
• Reconstituted peripherin-ROM1 tetramers induce membrane curvature.

Conclusions:

• The study provides a robust method for purifying and characterizing the peripherin-ROM1 complex.
• The tetrameric structure and membrane-bending capability of peripherin-ROM1 offer new insights into its role in photoreceptor outer segment morphogenesis.
• These findings are critical for understanding the molecular mechanisms underlying inherited retinal dystrophies associated with peripherin mutations.