The Supramolecular Organization of the G-Protein Coupled Receptor Rhodopsin in the Native Membrane

Light is collected by rod and cone receptor cells in the eye's retina to produce visual signals. Rods contain the receptor molecule rhodopsin, which triggers a chain reaction leading to a nerve impulse upon detection of light. A group of eye diseases named Retinitis Pigmentosa cause breakdown in the function of the rods and cones. Until recently, it was believed that rhodopsin functions as a single molecule. Our work demonstrated for the first time that rhodopsin exists in rows of pairs in its native environment [1-3]. Based on our result, we showed that disruption of rhodopsin's organization in the eye by specific mutations in the gene coding for rhodopsin may cause certain forms of the Retinitis Pigmentosa disease. Visualization of rhodopsin was performed by electron microscopy and particularly by a new sophisticated microscopy technique called atomic force microscopy. This discovery on the organization of rhodopsin led to a reconsideration of how the first steps in vision work. In addition, potential factors leading to the onset of Retinitis Pigmentosa diseases were established based on our structural data. Importantly, rhodopsin is just one example of a receptor type of which more than a thousand exist in the human body. It now seems likely that most of these receptors also function as paired molecules, which has many implications for our health.

Atomic force microscopy of native disk membranes isolated from mice. The deflection image and the surface topography (inset) reveal rows of rhodopsin dimers densely packed in paracrystalline arrays. The diameter of the round inset is 68 nm. The scale bar represents 250nm.

Contact:

Andreas Engel	Dimitrios Fotiadis
M.E. Müller Institute for Structural Biology Biozentrum, University of Basel Switzerland

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