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 Oestrogen regulates pathological changes of bones via bone lining cells
28.07.2017 | Veterinärmedizinische Universität Wien

nachricht Programming cells with computer-like logic
27.07.2017 | Wyss Institute for Biologically Inspired Engineering at Harvard

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Abrupt motion sharpens x-ray pulses

Spectrally narrow x-ray pulses may be “sharpened” by purely mechanical means. This sounds surprisingly, but a team of theoretical and experimental physicists developed and realized such a method. It is based on fast motions, precisely synchronized with the pulses, of a target interacting with the x-ray light. Thereby, photons are redistributed within the x-ray pulse to the desired spectral region.

A team of theoretical physicists from the MPI for Nuclear Physics (MPIK) in Heidelberg has developed a novel method to intensify the spectrally broad x-ray...

Im Focus: Physicists Design Ultrafocused Pulses

Physicists working with researcher Oriol Romero-Isart devised a new simple scheme to theoretically generate arbitrarily short and focused electromagnetic fields. This new tool could be used for precise sensing and in microscopy.

Microwaves, heat radiation, light and X-radiation are examples for electromagnetic waves. Many applications require to focus the electromagnetic fields to...

Im Focus: Carbon Nanotubes Turn Electrical Current into Light-emitting Quasi-particles

Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers

Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...

Im Focus: Flexible proximity sensor creates smart surfaces

Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.

At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...

Im Focus: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

 
Latest News

New 3-D imaging reveals how human cell nucleus organizes DNA and chromatin of its genome

28.07.2017 | Health and Medicine

Heavy metals in water meet their match

28.07.2017 | Power and Electrical Engineering

Oestrogen regulates pathological changes of bones via bone lining cells

28.07.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>