Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Rhodopsin on track

03.03.2015

Biological pigment aligns in double rows

Scientists from the caesar research center, an Institute of the Max Planck Society, have explained, with the help of electron microscopy, how the pigment rhodopsin is arranged in the rod cells of the retina. This question has long been subject of a heated scientific debate. The findings have been published in the scientific journal Structure. Future research on diseases causing blindness will be facilitated by this discovery.


The image shows a partially cut stack of discs from a mouse rod photoreceptor. The rhodopsin molecules in the disc membrane form dimers, the dimers form rows, and the rows are arranged in pairs, referred to as “tracks”. The tracks, with pre-assembled G protein transducin (green), are oriented parallel to the slit-shaped incisure of discs.

© caesar

Seeing starts in the rods and cones, two different types of sensory cells in the retina of the eye. The rods are responsible for dark vision and are particularly sensitive to light as a result. A single photon activates the pigment rhodopsin and initiates the process of vision. The rhodopsin molecules are found in flat membrane disks in the outer segment of photoreceptors.

The biochemical processes on which vision is based have been known for many years: rhodopsin triggers a highly-reinforced cascade of enzymatic reactions which give rise to electrical excitation. However, it was unclear up to now how the rhodopsin is arranged in these disks. For example, scientists debated whether rhodopsin arises as dimers, or whether the rhodopsin molecules wander around freely on the discs and thus encounter their interaction partners at random – like billiard balls following a wild hit with the cue.

Working in cooperation with Ashraf Al-Amoudi from the German Center for Neurodegenerative Diseases (DZNE), the researchers from the caesar research center used cryo-electron microscopy to examine the arrangement of rhodopsin in the rods of mice. This method involves the vitrification of the samples by shock-freezing, which conserves their natural structure. The actual examination of the sample is carried out using a cryo-transmission electron microscope which provides the resolution necessary to make individual molecules visible.

The team of scientists headed by Benjamin Kaupp and Ashraf Al-Amoudi succeeded in demonstrating that the rhodopsin molecules arise as dimers. In addition, the rhodopsin shows a supramolecular structure: the dimers are arranged in rows consisting of around 50 molecules. Two rows align to form double rows - like railway tracks. All rows are parallel in their arrangement.

The physiological function of such a regular arrangement is currently unclear. It is possible that the double rows form a platform, on which other molecules that participate in the electrical signal transformation, are also arranged regularly. The parallel arrangement could possibly explain polarisation vision, which is used by some vertebrates – for example amphibians and birds – to orient themselves in their environment.

Unlike the polarisation vision of insects, the corresponding mechanisms in vertebrates are still inadequately understood. Whether this capacity also exists in mammals remains a matter of dispute. The results on the mouse model will lead to further studies.

Contact

Prof. Dr. Ulrich Benjamin Kaupp
Associated Institute - Research Center caesar (center of advanced european studies and research), Bonn
Phone: +49 228 9656-100

Fax: +49 228 9656-111

Email: u.b.kaupp@caesar.de


Stefan Hartmann
Associated Institute - Research Center caesar (center of advanced european studies and research), Bonn
Phone: +49 228 9656-292

Fax: +49 228 9656-9292

Email: stefan.hartmann@caesar.de


Original publication
Gunkel, M., Schöneberg, J., Alkhaldi, W., Irsen, S., Noé, F., Kaupp, U.B. & Al-Amoudi, A.

Higher-order architecture of rhodopsin in intact photoreceptors and its implication for phototransduction kinetics

Structure, (doi: http://dx.doi.org/10.1016/j.str.2015.01.015)

Prof. Dr. Ulrich Benjamin Kaupp | Associated Institute - Research Center caesar (center of advanced european studies and research), Bonn

More articles from Life Sciences:

nachricht Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery
20.01.2017 | GSI Helmholtzzentrum für Schwerionenforschung GmbH

nachricht Seeking structure with metagenome sequences
20.01.2017 | DOE/Joint Genome Institute

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>