Quaternary organization of a phytochrome dimer as revealed by cryoelectron microscopy

Journal Article · Tue Jun 15 04:00:00 EDT 2010 · Proceedings of the National Academy of Sciences of the United States of America

DOI:https://doi.org/10.1073/pnas.1001908107· OSTI ID:1014318

Li, H; Li, H; Zhang, J; Vierstra, R D

Phytochromes are a collection of dimeric photoreceptors that direct a diverse array of responses in plants and microorganisms through photoconversion between a red light-absorbing ground state Pr, and a far-red light-absorbing photoactivated state Pfr. Photoconversion from Pr to Pfr is initiated by a light-driven rotation within the covalently attached bilin, which then triggers a series of protein conformational changes in the binding pocket. These movements ultimately affect an appended output module, which often has reversible protein kinase activity. Propagation of the light signal from the bilin to the output module likely depends on the dimerization interface but its architecture and response to phototransformation remain unclear. Here, we used single particle cryoelectron microscopy to determine the quaternary arrangement of the phytochrome dimer as Pr, using the bacteriophytochrome (BphP) from Deinococcus radiodurans. Contrary to the long-standing view that the two monomers are held together solely via their C-terminal region, we provide unambiguous evidence that the N-terminal bilin-binding region of BphP also provides a dimerization interface with the C-terminal kinase domain appearing as a more flexible appendage. The BphP monomers dimerize in parallel with the polypeptides intimately twisting around each other in a right-handed fashion. Based on this electron microscopic picture, we propose that the light-driven conformational changes transmitted from the chromophore to the output module along the spine of this extensive dimer interface is the central feature underpinning phytochrome signaling.

• Research Organization: BROOKHAVEN NATIONAL LABORATORY (BNL)
• Sponsoring Organization: LABORATORY-DIRECTED RESEARCH AND DEVELOPMENT
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1014318
• Report Number(s): BNL--93653-2010-JA; YN0100000
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America, Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Issue: 24 Vol. 107; ISSN 0027-8424; ISSN PNASA6
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
99 GENERAL AND MISCELLANEOUS
ARCHITECTURE
CONFORMATIONAL CHANGES
DIMERIZATION
DIMERS
ELECTRONS
GROUND STATES
MICROORGANISMS
MICROSCOPY
MONOMERS
PHOSPHOTRANSFERASES
PHYTOCHROMES
POLYPEPTIDES
PROTEINS
ROTATION
dimerization
histidine kinase
light signaling
signaling helix