Nav: Home

Photosynthesis involves a protein 'piston'

May 16, 2018

Osaka - Plants convert water and carbon dioxide into sugars and oxygen by photosynthesis. Photosynthesis is thus integral to life as we know it and has been investigated extensively by researchers around the globe.

However, photosynthesis is a complex microscopic process and some of its aspects are still not well understood. For example, Photosystem I (PSI) is a complicated protein system involved in photosynthesis. PSI reversibly forms complexes with ferredoxin (Fd) that mediate transfer of electrons derived from water. The PSI-Fd complex has not been fully characterized and the atomic-level interactions between PSI and Fd in the complex remain unclear despite their importance as links in the photosynthetic chain. This is because it is difficult to analyze the weak interactions in such an intricate protein system, which is partly caused by the weak binding interactions in the complex making it challenging to crystallize.

An Osaka University-led international collaboration recently made a breakthrough in knowledge of the PSI-Fd complex by collecting X-ray structural data for this complex isolated from a type of hot spring cyanobacteria. Genji Kurisu and collaborators grew bacteria, purified the PSI-Fd complex, and then grew crystals of the complex. X-ray data for the crystals were subsequently collected and resolved. The X-ray data for the complex provided some interesting information; in particular, that not all PSI-Fd interactions were the same. The results were reported in Nature Plants.

"We found that the crystal structure of the PSI-Fd complex contained two PSI trimers and six bound Fds in each crystallographic asymmetric unit," Kurisu says. "The Fds were non-equivalent because they were located at different distances from PSI; that is, Fd had strong and weak binding states in the PSI-Fd complex."

The group's findings were corroborated by the results of further characterization of the PSI-Fd complex by spectroscopic and chromatographic measurements, which also indicated that Fd had two different binding states in the complex. By considering all their experimental findings, the researchers developed a mechanism to explain the formation of two Fd binding states in the PSI-Fd complex.

"We propose that the binding of Fd to PSI lowers the symmetry of the three-dimensional structure of PSI," an associate professor, Hideaki Tanaka, in the team explains. "This induces a piston-like motion of one of the subunits of PSI to provide a complex that displays rapid electron transfer through PSI from the donor (Cyt c6) to the acceptor (Fd)."

The piston-like motion of the PSI subunit is thought to possibly act as a molecular signal across the cell membrane to stimulate rapid electron transfer.

The team's findings may provide clues to allow optimization of artificial photosynthesis to obtain complex chemicals from carbon dioxide, water, and light.
-end-
Osaka University was founded in 1931 as one of the seven imperial universities of Japan and now has expanded to one of Japan's leading comprehensive universities. The University has now embarked on open research revolution from a position as Japan's most innovative university and among the most innovative institutions in the world according to Reuters 2015 Top 100 Innovative Universities and the Nature Index Innovation 2017. The university's ability to innovate from the stage of fundamental research through the creation of useful technology with economic impact stems from its broad disciplinary spectrum.

Website: http://resou.osaka-u.ac.jp/en/top

Osaka University

Related Photosynthesis Articles:

Strange bacteria hint at ancient origin of photosynthesis
Structures inside rare bacteria are similar to those that power photosynthesis in plants today, suggesting the process is older than assumed.
Just how much does enhancing photosynthesis improve crop yield?
In the next two decades, crop yields need to increase dramatically to feed the growing global population.
Algal library lends insights into genes for photosynthesis
To identify genes involved in photosynthesis, researchers built a library containing thousands of single-celled algae, each with a different gene mutation.
New molecular blueprint advances our understanding of photosynthesis
Researchers at Lawrence Berkeley National Laboratory have used one of the most advanced microscopes in the world to reveal the structure of a large protein complex crucial to photosynthesis, the process by which plants convert sunlight into cellular energy.
How bacteria build hyper-efficient photosynthesis machines
Researchers facing a future with a larger population and more uncertain climate are looking for ways to improve crop yields, and they're looking to photosynthetic bacteria for engineering solutions.
More Photosynthesis News and Photosynthesis Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#537 Science Journalism, Hold the Hype
Everyone's seen a piece of science getting over-exaggerated in the media. Most people would be quick to blame journalists and big media for getting in wrong. In many cases, you'd be right. But there's other sources of hype in science journalism. and one of them can be found in the humble, and little-known press release. We're talking with Chris Chambers about doing science about science journalism, and where the hype creeps in. Related links: The association between exaggeration in health related science news and academic press releases: retrospective observational study Claims of causality in health news: a randomised trial This...