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 Nanocages in the lab and in the computer: how DNA-based dendrimers transport nanoparticles
19.10.2018 | University of Vienna

nachricht Less animal experiments on the horizon: Multi-organ chip awarded
19.10.2018 | Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Goodbye, silicon? On the way to new electronic materials with metal-organic networks

Scientists at the Max Planck Institute for Polymer Research (MPI-P) in Mainz (Germany) together with scientists from Dresden, Leipzig, Sofia (Bulgaria) and Madrid (Spain) have now developed and characterized a novel, metal-organic material which displays electrical properties mimicking those of highly crystalline silicon. The material which can easily be fabricated at room temperature could serve as a replacement for expensive conventional inorganic materials used in optoelectronics.

Silicon, a so called semiconductor, is currently widely employed for the development of components such as solar cells, LEDs or computer chips. High purity...

Im Focus: Storage & Transport of highly volatile Gases made safer & cheaper by the use of “Kinetic Trapping"

Augsburg chemists present a new technology for compressing, storing and transporting highly volatile gases in porous frameworks/New prospects for gas-powered vehicles

Storage of highly volatile gases has always been a major technological challenge, not least for use in the automotive sector, for, for example, methane or...

Im Focus: Disrupting crystalline order to restore superfluidity

When we put water in a freezer, water molecules crystallize and form ice. This change from one phase of matter to another is called a phase transition. While this transition, and countless others that occur in nature, typically takes place at the same fixed conditions, such as the freezing point, one can ask how it can be influenced in a controlled way.

We are all familiar with such control of the freezing transition, as it is an essential ingredient in the art of making a sorbet or a slushy. To make a cold...

Im Focus: Micro energy harvesters for the Internet of Things

Fraunhofer IWS Dresden scientists print electronic layers with polymer ink

Thin organic layers provide machines and equipment with new functions. They enable, for example, tiny energy recuperators. In future, these will be installed...

Im Focus: Dynamik einzelner Proteine

Neue Messmethode erlaubt es Forschenden, die Bewegung von Molekülen lange und genau zu verfolgen

Das Zusammenspiel aus Struktur und Dynamik bestimmt die Funktion von Proteinen, den molekularen Werkzeugen der Zelle. Durch Fortschritte in der...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Conference to pave the way for new therapies

17.10.2018 | Event News

Berlin5GWeek: Private industrial networks and temporary 5G connectivity islands

16.10.2018 | Event News

5th International Conference on Cellular Materials (CellMAT), Scientific Programme online

02.10.2018 | Event News

 
Latest News

Nanocages in the lab and in the computer: how DNA-based dendrimers transport nanoparticles

19.10.2018 | Life Sciences

Thin films from Braunschweig on the way to Mercury

19.10.2018 | Physics and Astronomy

App-App-Hooray! - Innovative Kits for AR Applications

19.10.2018 | Trade Fair News

VideoLinks
Science & Research
Overview of more VideoLinks >>>