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 At last, butterflies get a bigger, better evolutionary tree
16.02.2018 | Florida Museum of Natural History

nachricht New treatment strategies for chronic kidney disease from the animal kingdom
16.02.2018 | Veterinärmedizinische Universität Wien

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

Im Focus: Autonomous 3D scanner supports individual manufacturing processes

Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).

Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Fingerprints of quantum entanglement

16.02.2018 | Information Technology

'Living bandages': NUST MISIS scientists develop biocompatible anti-burn nanofibers

16.02.2018 | Health and Medicine

Hubble sees Neptune's mysterious shrinking storm

16.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>