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Spectroscopic and structural characteristics of a dual-light sensor protein, PYP-phytochrome related protein

  • Sum, Jia-Siang1
  • Yamazaki, Yoichi1
  • Yoshida, Keito1
  • Yonezawa, Kento2
  • Hayashi, Yugo1
  • Kataoka, Mikio1
  • Kamikubo, Hironari1, 2
  • 1 Division of Materials Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan
  • 2 Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
Published Article
Biophysics and Physicobiology
The Biophysical Society of Japan
Publication Date
Sep 01, 2020
DOI: 10.2142/biophysico.BSJ-2020015
PMID: 33194513
PMCID: PMC7610063
PubMed Central
  • Regular Article


PYP-phytochrome related (Ppr) protein contains the two light sensor domains, photoactive yellow protein (PYP) and bacteriophytochrome (Bph), which mainly absorb blue and red light by the chromophores of p -coumaric acid ( p CA) and biliverdin (BV), respectively. As a result, Ppr has the ability to photoactivate both domains together or separately. We investigated the photoreaction of each photosensor domain under different light irradiation conditions and clarified the inter-dependency between these domains. Within the first 10 s of blue light illumination, Ppr (Holo-Holo-Ppr) accompanied by both p CA and BV demonstrated spectrum changes reflecting PYPL accumulation, which can also be observed in Ppr containing only p CA (Holo-Apo-Ppr), and a fragment of Ppr lacking the C-terminal Bph domain. Although Holo-Apo-Ppr showed PYPL as a major photoproduct under blue light, as seen in the Bph-truncated Ppr, the equilibrium in the Holo-Holo-Ppr was shifted from PYPL to PYPM as the reaction progresses under blue light. Concomitantly, the spectrum of Bph exhibited subtle but distinguishable alteration. Together with the fact, it can be proposed that Bph with BV influences the photoreaction of PYP in Ppr, and vice versa. SAXS measurements revealed substantial tertiary structure changes in Holo-Holo-Ppr under continuous blue light irradiation within the first 5 min time domain. Interestingly, the changes in tertiary structure were partially suppressed by photoactivation of the Bph domain. These observations indicate that the photoreactions of the PYP and Bph domains are coupled with each other, and that the interplay realizes the structural switch, which might be involved in downstream signal transduction.

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