A long-sought goal: Crystallizing an elusive protein

March 25, 2013 by Dennis O'brien, Agricultural Research Service

Research associate Nathan Henderson (right) and Arizona State University professor Rebekka Wachter, both structural biochemists, examine a three-dimensional view (via X-ray crystallography) of rubisco activase from creosote bush. Credit: Mike Salvucci
(Phys.org) —Plants use an enzyme known as "rubisco" to capture carbon dioxide from the atmosphere and, with energy from the sun and nutrients from the soil, build up the shoots, leaves, and stems that make up the plant itself. Scientists have known that for years. They also have known that temperatures are important. When it gets too hot, a rubisco helper protein called "rubisco activase" shuts down, photosynthesis stops, and the plant stops growing. Heat literally unravels the activase protein, and when it does, the result is a less bountiful harvest. Different plants shut down photosynthesis at different temperatures, and the process of unraveling the activase protein is known as "denaturation."

Michael E. Salvucci, an Agricultural Research Service with the U.S. Arid-Land Agricultural Research Center, has teamed with Rebekka Wachter, associate professor of chemistry and biochemistry at Arizona State University, and Nathan Henderson, her postdoctoral research associate, to crystallize rubisco activase.

Crystallization will allow researchers to study the activase protein more closely, to visualize its structure, and possibly to manipulate its sequence so that it doesn't unravel at higher temperatures. The findings could help in the search for genes that cue plants to synthesize more heat-stable versions of the protein. Crops with such enhanced proteins could thrive at higher temperatures.

With expected to alter landscapes and growing cycles, the work is considered all the more relevant.

In Maricopa, Arizona, ARS plant physiologist Mike Salvucci and professor Rebekka Wachter from Arizona State University discuss strategies for isolating the enzyme rubisco activase from creosote bush, a heat-tolerant desert shrub. Credit: Nathan Henderson

The work builds on previous research by William L. Ogren and Archie R. Portis, Jr., two retired ARS scientists who were based in Urbana, Illinois, and Salvucci, who worked with them as a in the 1980s. The team discovered the existence of rubisco activase in 1985 and proved that it activates rubisco. For this and other accomplishments in the field of , Ogren was awarded the coveted International Alexander Von Humboldt Foundation Award. He was also named to the ARS Hall of Fame and to the National Academy of Sciences.

Scientific teams around the world have been trying to crystallize rubisco activase ever since. "You need to know what the protein looks like to understand how it works," Salvucci says. For proteins, the tougher and more rigid a structure, the easier it is to crystallize. But the problem has been that most plant activase proteins do not have rigid or even regular structures.

Wachter, Salvucci, and Henderson managed to crystallize the activase from the creosote bush, a shrub abundant in the Arizona desert. (The plant has no connection to the tarlike preservative found in many wood products.) They wanted to find the most temperature-tolerant activase possible, and they chose creosote because it can survive and photosynthesize at relatively high temperatures. Wachter's research is funded by a grant from the U.S. Department of Energy.

The researchers suspected creosote's activase proteins would remain relatively stable under most conditions. They cloned the plant's activase proteins and reproduced parts of them that were stable enough that could be produced from them.

The results were published in the Journal of Biological Chemistry.

Explore further: Shoe strings and egg openers

More information: "A Desert Shrub's Crystallized Protein Sheds Light on Photosynthesis" was published in the March 2013 issue of Agricultural Research magazine.

Related Stories

Shoe strings and egg openers

November 8, 2011

Photosynthesis is one of the most important biological processes. However, it is less efficient in plants than it could be. Red algae, in contrast, use a slightly different mechanism and are thus more productive. Scientists ...

Chaperones for climate protection

January 14, 2010

(PhysOrg.com) -- The World Climate Conference recently took place. Reports about carbon dioxide levels, rising temperatures and melting glaciers appear daily. Scientists from the Max Planck Institute (MPI) of Biochemistry ...

Nitric oxide regulates plants as well as people

April 28, 2008

Nitric oxide has emerged as an important signaling molecule in plants - as in mammals including people. In studies of a tropical medicinal herb as a model plant, researchers have found that nitric oxide targets a number of ...

Scientists discover genetic key to efficient crops

January 24, 2013

(Phys.org)—With projections of 9.5 billion people by 2050, humankind faces the challenge of feeding modern diets to additional mouths while using the same amounts of water, fertilizer and arable land as today.

Recommended for you

3-D culturing hepatocytes on a liver-on-a-chip device

January 17, 2019

Liver-on-a-chip cell culture devices are attractive biomimetic models in drug discovery, toxicology and tissue engineering research. To maintain specific liver cell functions on a chip in the lab, adequate cell types and ...

This computer program makes pharma patents airtight

January 17, 2019

Routes to making life-saving medications and other pharmaceutical compounds are among the most carefully protected trade secrets in global industry. Building on recent work programming computers to identify synthetic pathways ...

Cultivating 4-D tissues—the self-curving cornea

January 17, 2019

Scientists at Newcastle University have developed a biological system which lets cells form a desired shape by moulding their surrounding material—in the first instance creating a self-curving cornea.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.