While watching the light leads to obvious, a multi-step chemical process. At the end of a nerve impulse that gives the impression of light into the brain. It starts with the interaction of light with the rhodopsin protein. Researchers at the Paul Scherrer Institute is now able to decide together with colleagues in the UK and the U.S., the exact structure of this short-term Rhodopsin moleküls excited state and to provide an accurate picture of the first stage of visual processing .
This result should provide a better understanding of hereditary retinitis pigmentosa eye disease and may indicate pathways for handling or deceleration. At the same time, provides the result is the basis for understanding many other processes in the body, based on a similar mechanism - such as the perception of odors and process control by hormones. About the results, the researchers report in the online edition of the journal Nature.
This result should provide a better understanding of hereditary retinitis pigmentosa eye disease and may indicate pathways for handling or deceleration. At the same time, provides the result is the basis for understanding many other processes in the body, based on a similar mechanism - such as the perception of odors and process control by hormones. About the results, the researchers report in the online edition of the journal Nature.
Seeing is a very complex process - a variety of chemical reactions that occur before the visit comes to our consciousness. At the beginning of this process, the light hits the retina Sehsinneszellen in the eye - the pins or rods. In the cell membranes of the rods, which are responsible for vision in low light, rhodopsin molecules are sitting - real light sensors. They consist of seven parts, rod-shaped molecule that extends from outside to inside the cell. When light from the outside of the rhodopsin, changed the arrangement of rod-shaped pieces, so that within the cell a molecule called a G protein takes place in the middle. The coupling of G protein activates a cascade of events that are activated at the end of a nerve impulse.
The pigment is very sensitive to light is the retina - a form of vitamin A - which puts a small molecule increased between the seven parties of rhodopsin. When light falls on it, it also stretches and pushes parts of rhodopsin, the creation of spaces for G-protein. Now, researchers at the Paul Scherrer managed institution, to determine the structure of rhodopsin in the activated state - in order to modify the light in the shape of the retina extended. This condition is actually very short, since rhodopsin themselves as soon as possible back to the state, in which is sensitive to light. The ISP, however, researchers have found a way to change the molecule a bit to keep the active form of more time and were able to determine its structure. The structure of the inactive form of rhodopsin, which occurs without light, was already known. With knowledge of both structures are able to understand exactly how the visual system in the eye begins at the molecular level.
For inquiries, these molecules are produced in large quantities and regularly arranged in a crystalline structure. This rhodopsin is a membrane protein very few of this kind, which can crystallize. The crystals were illuminated with synchrotron light and the deflection of light on the way through the glass, the researchers deduced the structure of molecules. The measurements were made in the SLS Synchrotron Light Source at the Paul Scherrer Institute in Switzerland and two similar facilities.
Universal mechanisms to understand life
The investigation of rhodopsin helps to a large class of similar molecules to understand -. There are over 800 of them in people, "said Joerg stand, head of the research project" The majority do not react to light, but compliant to other stimuli and thus the diversity Responsibilities: In the sense of smell, they react to substances in the air. Or that serve as receptors for hormones in the body -. such as beta-receptors, which are in central control of blood pressure in part responsible "These serve as docking site for the well-known as a beta blocker against high blood pressure. In general, these molecules are of great interest for pharmaceutical research because it can be controlled through processes in the body or block very well targeted. Therefore able to interact, such as drugs used in cardiac rhythm disorders, migraines, allergies to these receptors. The exact structure of beta-receptors was the subject of another study conducted by researchers at the Paul Scherrer Institute with colleagues from Cambridge, recently published in Nature.
Improved therapies for eye disease
"Our experience with the structural study of modified rhodopsin molecules are currently spending for research into common eye disease - retinitis pigmentosa,"said Stand. In this inherited disease is often the rhodopsin in the cones of the eye is changed, not like in the good eye completely renewed regularly - always being part of the "old" molecules, which gradually poison the visual cells. This principle leads to night blindness, and for a long time in a very limited field of view. Stand, ". In the future we will be able to determine exactly has changed the way that the rhodopsin in the disease, and then examine the so tiny molecules, which are drugs, the disease can be incorporated into the rhodopsin" Could use this knowledge in the computer to optimize the structure of specific drugs.
Research International
Jörg support and the head of the Biomolecular Research Laboratory Paul Scherrer Institute, Professor Gebhard Schertler started the project in the Laboratory of Molecular Biology of the MRC in Cambridge (England) and completed after his transfer to the ISP to an end. They have worked in close collaboration with colleagues at Brandeis University, USA.
Text: Paul Piwnicki
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