Scientists from Charité -- Universitätsmedizin Berlin, in cooperation with the Humboldt-University of Berlin as well as Universities in South Korea, London and Toronto, have made a breakthrough in the basics of signal transduction research. They were able to clarify for the first time, in an important information carrier in the human body, the receptor protein rhodopsin, how such a protein must be designed to accommodate a light signal.
The study is published in the journal Nature.
Rhodopsin is one of the so-called G protein-coupled receptors. These proteins are found in the membranes that envelop every living cell. They connect the cells with signals from the environment such as light, scents and flavors, but also with signals from the body, such as hormones. Therefore, they are involved in almost all physiological processes in the body as well as in most diseases. In order for a receptor like Rhodopsin to receive information, it must interact with molecular carriers of information -- as for example a hormone or a light-sensitive "antenna." This is only possible when the receptor forms a binding site, in which the binding molecule (the so-called ligand) fits.
The research group has succeeded, for the first time, in keeping the light receptor rhodopsin in its light-activated state and in a stable form. In this so-called Meta State, the receptor binds the retinal, a derivative of vitamin A, in a form that is transformed by light. With this structure in hands, one gains insights into the mechanism of the interaction between the receptor and its ligand.
This is a significant step forward in the clarification and understanding of signal transduction in the cell. "One can learn from our example how a ligand is "interrogated" by a receptor protein ," explains Prof. Hofmann, deputy Director of the Institute of Medical Physics and Biophysics and Member of the Centre for Biophysics and Bioinformatics of the Humboldt-University. "There is reason to believe that the basic processes in ligand binding are similar in different receptors. Of course we also hope that we will benefit from the understanding of the underlying structures and mechanisms for the treatment of pathological changes in signal transduction."
- Hui-Woog Choe, Yong Ju Kim, Jung Hee Park, Takefumi Morizumi, Emil F. Pai, Norbert Krauß, Klaus Peter Hofmann, Patrick Scheerer, Oliver P. Ernst. Crystal structure of metarhodopsin II. Nature, 2011; DOI: 10.1038/nature09789
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