Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Shedding light on a photosensitive protein

07.11.2011
Special techniques for handling membrane proteins provide insight into the structure and function of an algal light-sensing molecule

Even without eyes, many single-celled organisms can perceive and react to light. This is achieved via rhodopsins, proteins at the cell surface that trigger responses to specific wavelengths of light by directing the flow of ions into or out of the cell.


Figure 1: Crystal structure of ARII, a light-activated proton pump from the algae Acetabularia acetabulum. Copyright : 2011 Shigeyuki Yokoyama

Naoki Kamo’s group at Matsuyama University in Ehime recently began working with ARII, a gene encoding a rhodopsin from the algae Acetabularia acetabulum. The encoded ARII protein proved extremely difficult to characterize and its function was initially ambiguous. However, Kamo’s team found success by joining forces with Shigeyuki Yokoyama’s group at the RIKEN Systems and Structural Biology Center in Yokohama.

To reveal a protein’s structure and function, scientists typically generate highly ordered crystals of that protein and then analyze the diffraction pattern that results when the crystals are bombarded with x-rays. Membrane proteins will fold only under very specific conditions, but Yokoyama’s team devised a ‘cell-free’ system that provides tight control over protein manufacture2. By mixing the cellular protein synthesis machinery with lipids and detergents, they were able to achieve an environment highly hospitable to ARII production.

“This tough target could be expressed very efficiently using our cell-free protein synthesis system, even to the same degree as easy, soluble proteins,” says Yokoyama. He was subsequently able to rapidly purify the resulting protein and obtained a high-resolution structure for ARII by crystallizing it in the presence of lipid molecules (Fig. 1).

ARII proved to be relatively similar to bacteriorhodopsin (BR), a proton pump from the archaeal species Halobacterium salinarum. Preliminary analysis of ARII suggested that this protein likewise acts to transport protons from the cytoplasm to the exterior of the cell in response to illumination.

By analyzing the ARII structure, the researchers were able to identify a network of amino acids that directly participate in the uptake and release of individual protons. There are some notable differences in the kinetics of proton transport between BR and ARII. Kamo and Yokoyama also noted subtle structural disparities that might explain why ARII releases its protons ‘late’ relative to the rapid release observed with BR.

Having demonstrated the effectiveness of this membrane protein synthesis approach, the researchers are now delving deeper into the structure and function of ARII and ARI, another rhodopsin expressed by A. acetabulum. “We will produce various mutants with this efficient cell-free system and use many biophysical methods to understand the detailed proton transport mechanism and physiological roles of ARI and ARII,” says Yokoyama.

The corresponding author for this highlight is based at the Systems and Structural Biology Research Team, RIKEN Systems and Structural Biology Center

References:

Wada, T., Shimono, K., Kikukawa, T., Hato, M., Shinya, N., Kim, S.Y., Kimura-Someya, T., Shioruzu, M., Tamogami, J., Miyauchi, S. et al. Crystal structure of the eukaryotic light-driven proton-pumping rhodopsin, Acetabularia rhodopsin II, from marine alga. Journal of Molecular Biology 411, 986–998 (2011). article

Shimono, K., Goto, M., Kikukawa, T., Miyauchi, S., Shirouzu, M., Kamo, N. & Yokoyama, S. Production of functional bacteriorhodopsin by an Eschericihia coli cell-free protein synthesis system supplemented with steroid detergent and lipid. Protein Science 18, 2160–2171 (2009). article

gro-pr | Research asia research news
Further information:
http://www.riken.jp
http://www.researchsea.com

More articles from Life Sciences:

nachricht New risk factors for anxiety disorders
24.02.2017 | Julius-Maximilians-Universität Würzburg

nachricht Stingless bees have their nests protected by soldiers
24.02.2017 | Johannes Gutenberg-Universität Mainz

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

Stingless bees have their nests protected by soldiers

24.02.2017 | Life Sciences

New risk factors for anxiety disorders

24.02.2017 | Life Sciences

MWC 2017: 5G Capital Berlin

24.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>