Cryo-electron microscopy structures of human cone visual pigments.

Area of Science:

• Molecular biology
• Structural biology
• Vision science

Background:

• Human color vision depends on three cone opsins (LWS, MWS, SWS) and rhodopsin mediates rod vision.
• While rhodopsin's structure is known, human cone opsin structures remained elusive.

Purpose of the Study:

• To determine the structures of human cone opsins in their active states.
• To elucidate the structural basis for spectral sensitivity tuning and rod-cone differences.

Main Methods:

• Cryo-electron microscopy was used to capture the structures.
• Structures were determined for all three human cone opsins bound to G protein and all-trans retinal.

Main Results:

• The three human cone opsin structures were resolved in an active conformation.
• Cone opsins exhibit significant structural differences compared to rhodopsin.
• Unique features like a counterion site (LWS/MWS) and serine ring (SWS) were identified in the retinal binding pocket.

Conclusions:

• The determined structures provide insight into the molecular mechanisms of human color vision.
• These findings clarify how amino acid substitutions influence spectral sensitivity.
• The structures aid in understanding color vision deficiencies and rod-cone activation disparities.