Berkeley Lab Study Shows Orange Carotenoid Protein Shifts More Than Just Color for Cyanobacterial Photoprotection
In a study led by Cheryl Kerfeld, a structural biologist who holds joint appointments with Berkeley Lab’s Physical Biosciences Division and Michigan State University, the research team found that in cyanobacteria the energy-quenching mechanism is triggered by an unprecedented, large-scale movement (relatively speaking) from one location to another of the carotenoid pigment within a critical light-sensitive protein called the Orange Carotenoid Protein (OCP). As a result of this translocation, the carotenoid changes its shape slightly and interacts with a different set of amino acid neighbors causing the protein to shift from an “orange” light-absorbing state to a “red” photoprotective state. This turns out to be an unanticipated molecular priming event in photoprotection.
“Prior to our work, the assumption was that carotenoids are static, held in place by the protein scaffold,” Kerfeld says. “Having shown that the translocation of carotenoid within the protein is a functional trigger for photoprotection, scientists will need to revisit other carotenoid-binding protein complexes to see if translocation could play a role in those as well. Understanding the dynamic function of carotenoids should be useful for the design of future artificial photosynthetic systems.”
"This new species has a growth form and gene sequence so unusual that it does not fit into any of the existing families," said Susan Wilde, the Warnell professor who has been leading the research. "The naming convention for cyanobacteria is to use Greek for the genus—Aetokthonos translates to ‘eagle-killer.' The species name is always Latin, and hydrillicola means ‘lives on hydrilla.'"
Beginning in the mid-1990s, American bald eagles started to die off in noticeable numbers from a neurological disease called avian vacuolar myelinopathy. AVM was first found in Arkansas in 1994, but over the past two decades, 160 eagles are known to have died across the Southeast from the disease, including 80 from one Georgia impoundment on the Savannah River, the J. Strom Thurmond Reservoir.
For the first time in history, researchers were able to observe a chemical bond being born.
Using an X-ray laser at the Department of Energy's SLAC National Accelerator Laboratory, scientists caught their first glimpse of the transition state in which two atoms begin to form a weak bond in the first steps of transforming into a molecule.