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 Antimicrobial substances identified in Komodo dragon blood
23.02.2017 | American Chemical Society

nachricht New Mechanisms of Gene Inactivation may prevent Aging and Cancer
23.02.2017 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

From rocks in Colorado, evidence of a 'chaotic solar system'

23.02.2017 | Physics and Astronomy

'Quartz' crystals at the Earth's core power its magnetic field

23.02.2017 | Earth Sciences

Antimicrobial substances identified in Komodo dragon blood

23.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>