This animation gives a 360-degree view of the phycobilisome structure researchers helped reveal. Credit: The Kerfeld Lab/Nature
This story is adapted from a news release from Michigan State University
-By Matt Davenport
Researchers at Michigan State University (MSU), UC Berkeley, the University of Southern Bohemia, and Lawrence Berkeley National Laboratory (Berkeley Lab) have helped reveal the most detailed picture to date of important biological "antennae."
Nature has evolved these structures to harness the sun's energy through photosynthesis, but these sunlight receivers don't belong to plants. They're found in microbes known as cyanobacteria, the evolutionary descendants of the first organisms on Earth capable of taking sunlight, water, and carbon dioxide and turning them into sugars and oxygen.
Published this week in the journal Nature, the findings immediately shed new light on microbial photosynthesis - specifically how light energy is captured and sent to where it's needed to power the conversion of CO2 into sugars. Going forward, the insights could also help researchers remediate harmful algal blooms, develop artificial photosynthesis systems for renewable energy, and enlist microbes in sustainable manufacturing that starts with the raw materials of CO2 and sunlight.
"There's a lot of interest in using cyanobacteria as solar-powered factories that capture sunlight and convert it into a kind of energy that can be used to make important products," said Cheryl Kerfeld, a member of the MSU-DOE Plant Research Laboratory, which is supported by the U.S. Department of Energy. "With a blueprint like the one we've provided in this study, you can start thinking about tuning and optimizing the light-harvesting component of photosynthesis."
"Once you see how something works, you have a better idea of how you can modify it and manipulate it. That's a big advantage," said Markus Sutter, a senior research associate in the Kerfeld Lab, which operates at MSU and Berkeley Lab.
The researchers uncovered an unparalleled level of detail in the phycobilisome, which cyanobacteria use in photosynthesis. Its constituent protein and pigment structures are shown as the blue and green assemblies in this illustration. The OCP, the occasional orange hangers-on, help dissipate excess captured energy as heat. Credit: Janet Iwasa/University of Utah
The cyanobacterial antenna structures, called phycobilisomes, are complex collections of pigments and proteins, which assemble into relatively massive complexes.
For decades, researchers have been working to visualize the different building blocks of phycobilisomes to understand how they're put together. Phycobilisomes are fragile, necessitating this piecemeal approach. Historically, researchers have been unable to get the high-resolution images of intact antennae needed to understand how they capture and conduct light energy.
Now, thanks to an international team of experts and advances in cryogenic electron microscopy (cryo-EM), the structure of a cyanobacterial light harvesting antenna is available with nearly atomic resolution.
"We were fortunate to be a team made up of people with complementary expertise, people who worked well together," said Kerfeld, who is also a professor of structural bioengineering at MSU. "The group had the right chemistry."
'A long journey, full of surprises'
"This work is a breakthrough in the field of photosynthesis," said Paul Sauer, a postdoctoral researcher in UC Berkeley Professor Eva Nogales' cryo-EM lab. Nogales is also a senior faculty scientist in Berkeley Lab's Biosciences Area.
"The complete light-harvesting structure of a cyanobacteria's antenna has been missing until now," Sauer said. "Our discovery helps us understand how evolution came up with ways to turn CO2 and light into oxygen and sugar in bacteria, long before any plants existed on our planet."
