title: Local and global structural drivers for the photoactivation of the orange carotenoid protein.
abstract: Photoprotective mechanisms are of fundamental importance for the survival of photosynthetic organisms. In cyanobacteria, the orange carotenoid protein (OCP), when activated by intense blue light, binds to the light-harvesting antenna and triggers the dissipation of excess captured light energy. Using a combination of small angle X-ray scattering (SAXS), X-ray hydroxyl radical footprinting, circular dichroism, and H/D exchange mass spectrometry, we identified both the local and global structural changes in the OCP upon photoactivation. SAXS and H/D exchange data showed that global tertiary structural changes, including complete domain dissociation, occur upon photoactivation, but with alteration of secondary structure confined to only the N terminus of the OCP. Microsecond radiolytic labeling identified rearrangement of the H-bonding network associated with conserved residues and structural water molecules. Collectively, these data provide experimental evidence for an ensemble of local and global structural changes, upon activation of the OCP, that are essential for photoprotection.
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720;
authors.forename: Sayan
authors.initials: S
authors.lastname: Gupta
authors.affiliation: Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195;
authors.forename: Miklos
authors.initials: M
authors.lastname: Guttman
authors.affiliation: Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824;
authors.forename: Ryan L
authors.initials: RL
authors.lastname: Leverenz
authors.affiliation: School of Science and Technology, Nazarbayev University, Astana 010000, Kazakhstan;
authors.forename: Kulyash
authors.initials: K
authors.lastname: Zhumadilova
authors.affiliation: Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824;
authors.forename: Emily G
authors.initials: EG
authors.lastname: Pawlowski
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720;
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Petzold
authors.affiliation: Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195;
authors.forename: Kelly K
authors.initials: KK
authors.lastname: Lee
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720;
authors.forename: Corie Y
authors.initials: CY
authors.lastname: Ralston
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720; Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824; Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720; Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824 ckerfeld@lbl.gov.
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Kerfeld
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D046939:Synechocystis / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; C109473:orange carotenoid protein, Synechocystis
keywords: SAXS; X-ray footprinting; hydrogen deuterium exchange; orange carotenoid protein; photoprotection