期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 107, 期 24, 页码 10872-10877出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1001908107
关键词
dimerization; histidine kinase; light signaling; signaling helix
资金
- Brookhaven National Laboratory Laboratory-Directed Research and Development
- National Institutes of Health [GM74985]
- National Science Foundation [MCB-07191530]
- University of Wisconsin-Madison College of Agricultural and Life Science
- Direct For Biological Sciences
- Div Of Molecular and Cellular Bioscience [1022010] Funding Source: National Science Foundation
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 photo-transformation 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 longstanding 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.
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