5c5k
From Proteopedia
Structure of the Pfr form of a canonical phytochrome
Structural highlights
Function[BPHY_DEIRA] Photoreceptor which exists in two forms that are reversibly interconvertible by light: the R form that absorbs maximally in the red region of the spectrum and the FR form that absorbs maximally in the far-red region. Has also a slight blue shift for the far-red maximum. Could also absorb green light. May participate in regulating pigment synthesis like the carotenoid deinoxanthin which could protect the bacterium from intense visible light. Publication Abstract from PubMedPhytochromes are photochromic photoreceptors responsible for a myriad of red/far-red light-dependent processes in plants and microorganisms. Interconversion is initially driven by photoreversible isomerization of bilin, but how this alteration directs the photostate-dependent changes within the protein to actuate signaling is poorly understood. Here, we describe the structure of the Deinococcus phytochrome photosensory module in its near complete far-red light-absorbing Pfr state. In addition to confirming the 180 degrees rotation of the D-pyrrole ring, the dimeric structure clearly identifies downstream rearrangements that trigger large-scale conformational differences between the dark-adapted and photoactivated states. Mutational analyses verified the importance of residues surrounding the bilin in Pfr stabilization, and protease sensitivity assays corroborated photostate alterations that propagate along the dimeric interface. Collectively, these data support a cooperative "toggle" model for phytochrome photoconversion and advance our understanding of the allosteric connection between the photosensory and output modules. Crystal Structure of Deinococcus Phytochrome in the Photoactivated State Reveals a Cascade of Structural Rearrangements during Photoconversion.,Burgie ES, Zhang J, Vierstra RD Structure. 2016 Jan 28. pii: S0969-2126(16)00009-5. doi:, 10.1016/j.str.2016.01.001. PMID:26853942[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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