Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Purdue biologists’ spotlight solves mysteries of photosynthesis, metabolism

06.10.2003


The Purdue University biologists who determined the structure of the cytochrome protein complex, which is critical for photosynthesis, are, from left, professor Janet Smith, associate research scientist Huamin Zhang, visiting scholar Genji Kurisu and distinguished professor William Cramer. (Purdue Department of Biological Sciences photo/T. Geders)


Shown is an illustration of the cytochrome b6f protein complex, which is critical for photosynthesis. The eight colors represent the eight protein components of the cytochrome complex; the cylinders are the 26 segments of the complex that cross the photosynthetic membrane; the colored rings made of little balls that are embedded in protein are the groups that actually carry the electrons stimulated by light absorbed in photosynthesis. Purdue University biologists determined the structure of the complex using X-ray crystallography. (Purdue Department of Biological Sciences illustration/H. Zhang)


A complete molecular-scale picture of how plants convert sunlight to chemical energy has been obtained at Purdue University, offering potential new insights into animal metabolism as well.

Using advanced imaging techniques, a team of Purdue biologists has determined the structure of the cytochrome, a protein complex that governs photosynthesis in a blue-green bacterium. While their work does not immediately suggest any industrial applications, it does reveal a wealth of information not only about a chemical process crucial to all life on the planet, but also about how cells handle and distribute energy. According to team member William Cramer, the study is a great leap forward in our understanding of photosynthesis.

"Where we once could see merely the tip of the iceberg, we can now perceive the entire mechanism of photosynthesis," said Cramer, the Henry Koffler Distinguished Professor of Biological Sciences in Purdue’s School of Science. "Before we found a way to crystallize the cytochrome, we had a general picture of the photosynthetic process, but possessed only a fraction of a percent of the information we now have. Now that we can examine these proteins closely with X-ray crystallography, it could lead to knowledge about how all cells exchange energy with their environment."



Cramer also said that the study is an important contribution to the young field of proteomics research because there is little data on the important family of membrane-embedded proteins in the total protein database.

"Membrane proteins are involved in a cell’s interactions with its environment, making them an essential component of metabolism," he said. "However, they are difficult to crystallize for study. This research could clarify our understanding of energy flow in human cells as well, giving us better insight into respiration and the absorption of antioxidants in animal cells."

The report appears today (Thursday, 10/2) in the journal Science’s online edition, Science Express. The first two authors on the manuscript are Genji Kurisu, visiting scholar from Osaka University, Japan, and Huamin Zhang, associate research scientist in the Department of Biological Sciences at Purdue, who made major contributions to the crystallographic and biochemical part of the analysis.

The report paints a picture of the complex motion of electrons and protons across the bacterium’s cell membrane, the boundary between the cell and its surroundings.

"Plant cell membranes are like the two ends of a battery," said Janet Smith, professor of biological sciences and the team member responsible for much of the structure analysis. "They are positive on the inside and negative on the outside, and they are charged up when solar energy excites electrons from hydrogen within the cell. The electrons travel up into the cell membrane via proteins that conduct them just like wires. Of course, because of their high energy level, the electrons want to ’fall back’ like water over a dam, releasing the energy a plant harnesses to stay alive."

While this general picture has been common knowledge to scientists for decades, the complex motion of electrons and protons in the membrane have not.

"It’s a bit like watching electrons move through a computer chip," Smith said. "A microprocessor has far more complex and numerous routes for its electricity to follow than, say, a flashlight, which only has one. But while a chip uses electrons to flip tiny digital switches back and forth for calculations, the membrane uses them to drive the cell’s metabolism."

The cell that provided the proteins for the team’s work was a cyanobacterium, a single-celled thermophile plant commonly found in hot springs such as those in Yellowstone. The particular cyanobacterium used in these studies was isolated by Swiss researchers at a hot spring in Iceland.

While animals do not employ photosynthesis, their cells do make use of similar proteins for respiration. The similarities could lead to a better understanding of our own metabolic processes.

"What we see when we examine these proteins is the nature of their partial similarity," said Cramer. "The differences can now be explored more easily."

Examining the membrane proteins has itself been the challenge for the research team, which is reaping the benefits of its breakthrough work with protein crystallization. While proteomics specialists have been crystallizing protein molecules for years to obtain their structure, membrane proteins have proven difficult because they do not dissolve in water, a crucial step in the crystallization process.

"This difficulty has left a gap in our knowledge of membrane proteins, which total about 30 percent of the proteins in living things," Cramer said. "After finding a way to crystallize a membrane protein earlier this year, it only took a few months before we were able to look at photosynthesis in such detail."

The team is hopeful that their method can be applied to other membrane proteins, which they consider a variety of vast untapped potential.

"If cells were countries, membrane proteins would control all the international commerce," Cramer said. "They are the border guards that regulate all the energy transfer and material exchange across the boundary between the cell and its environment. If you want to get a drug into a cell where it can be of use, you have to deal with the membrane proteins – that’s why they’re so tempting a subject to study."

Funding for the research was provided in part by the National Institute of General Medical Sciences (NIGMS), a branch of the National Institutes of Health. NIGMS’s Dr. Peter Preusch agreed with Cramer’s assessment of the value of membrane protein research, saying the team’s work could lead to significant discoveries.

"New insights provided by Dr. Cramer’s elegant studies underscore the value of searching for biological secrets in model systems," he said. "The findings will advance the study of energy metabolism in humans."

Members of the team are affiliated with several research centers at Purdue, including the Markey Center for Structural Biology, the Bindley Bioscience Center at Discovery Park, the Interdepartmental Program in Biochemistry and Molecular Biology, and the Purdue Cancer Center.

Writer: Chad Boutin, (765) 494-2081, cboutin@purdue.edu

Sources: William Cramer, (765) 494-4956, wac@bilbo.bio.purdue.edu

Janet Smith, (765) 494-9246, smithj@purdue.edu

Purdue News Service: (765) 494-2096; purduenews@purdue.edu

Chad Boutin | Purdue News
Further information:
http://news.uns.purdue.edu/html4ever/031002.Cramer.photo.html
http://news.uns.purdue.edu/UNS/html4ever/030505.Cramer.crystal.html

More articles from Life Sciences:

nachricht Research team creates new possibilities for medicine and materials sciences
22.01.2018 | Humboldt-Universität zu Berlin

nachricht Saarland University bioinformaticians compute gene sequences inherited from each parent
22.01.2018 | Universität des Saarlandes

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Thanks for the memory: NIST takes a deep look at memristors

22.01.2018 | Materials Sciences

Radioactivity from oil and gas wastewater persists in Pennsylvania stream sediments

22.01.2018 | Earth Sciences

Saarland University bioinformaticians compute gene sequences inherited from each parent

22.01.2018 | Life Sciences

VideoLinks Wissenschaft & Forschung
Overview of more VideoLinks >>>