Time-Resolved Infrared Spectroscopy on Plant Cryptochrome—Relevance of Proton Transfer and ATP Binding for Signaling

Schröder L, Oldemeyer S, Kottke T (2018)
The Journal of Physical Chemistry A 122(1): 140-147.

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Abstract / Notes
Plant cryptochromes are light receptors in land plants and algae with very diverse functions such as circadian timing and lifecycle progression. The receptor consists of a photolyase homology region (PHR) binding the flavin chromophore and a C-terminal extension (CCT) responsible for signaling. The reputed signaling state, the flavin neutral radical, is formed by a femtosecond electron transfer and microsecond proton transfer to the excited, oxidized flavin. Subsequently, a 500 μs loss of β-sheet structure ∼25 Å away from flavin was resolved and suggested to be part of the signal conduction to the CCT. Here, we performed time-resolved, step-scan Fourier transform IR spectroscopy on the PHR of the plant cryptochrome pCRY (formerly CPH1) from Chlamydomonas reinhardtii. In a mutant lacking the proton donor aspartic acid 396 only the flavin anion radical is formed, but we observed the loss of β-sheet structure with a time constant of 1.3 ms, similar to the 500 μs of the wild type. This finding implies that the anion radical may be considered signaling-competent. In the steady state, a variation of external pH up to 8.3 did not have any effect on the difference spectra including the protonated state of Asp396. However, we detected the prominent loss of β-sheet structure by illumination only in the presence of adenosine triphosphate (ATP). We conclude that the bound ATP stabilizes these light-induced changes in secondary structure to ensure a physiological lifetime compatible with signaling by plant cryptochrome.
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Schröder L, Oldemeyer S, Kottke T. Time-Resolved Infrared Spectroscopy on Plant Cryptochrome—Relevance of Proton Transfer and ATP Binding for Signaling. The Journal of Physical Chemistry A. 2018;122(1):140-147.
Schröder, L., Oldemeyer, S., & Kottke, T. (2018). Time-Resolved Infrared Spectroscopy on Plant Cryptochrome—Relevance of Proton Transfer and ATP Binding for Signaling. The Journal of Physical Chemistry A, 122(1), 140-147. doi:10.1021/acs.jpca.7b10249
Schröder, L., Oldemeyer, S., and Kottke, T. (2018). Time-Resolved Infrared Spectroscopy on Plant Cryptochrome—Relevance of Proton Transfer and ATP Binding for Signaling. The Journal of Physical Chemistry A 122, 140-147.
Schröder, L., Oldemeyer, S., & Kottke, T., 2018. Time-Resolved Infrared Spectroscopy on Plant Cryptochrome—Relevance of Proton Transfer and ATP Binding for Signaling. The Journal of Physical Chemistry A, 122(1), p 140-147.
L. Schröder, S. Oldemeyer, and T. Kottke, “Time-Resolved Infrared Spectroscopy on Plant Cryptochrome—Relevance of Proton Transfer and ATP Binding for Signaling”, The Journal of Physical Chemistry A, vol. 122, 2018, pp. 140-147.
Schröder, L., Oldemeyer, S., Kottke, T.: Time-Resolved Infrared Spectroscopy on Plant Cryptochrome—Relevance of Proton Transfer and ATP Binding for Signaling. The Journal of Physical Chemistry A. 122, 140-147 (2018).
Schröder, Lea, Oldemeyer, Sabine, and Kottke, Tilman. “Time-Resolved Infrared Spectroscopy on Plant Cryptochrome—Relevance of Proton Transfer and ATP Binding for Signaling”. The Journal of Physical Chemistry A 122.1 (2018): 140-147.
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PMID: 29210583
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