Special seminar: Remote-controlled protonation reaction enables ultrafast structural changes in a photoreceptor protein

Name: Madan Kumar Shankar

Affiliation: Faculty of Biophysics, Biochemistry and Biotechnology, Jagiellonian University, Krakow, Poland

 Title: Remote-controlled protonation reaction enables ultrafast structural changes in a photoreceptor protein

Date & Time: Wednesday, 19^th February 2025 at 02:00 p.m.

Microsoft Teams Link: https://teams.microsoft.com/l/meetup-join/19%3ameeting_ODJjZTEwMWEtYTRkYi00ZjhhLWIyZGMtNWYwOWJiNTNjYzRm%40thread.v2/0?context=%7b%22Tid%22%3a%226f15cd97-f6a7-41e3-b2c5-ad4193976476%22%2c%22Oid%22%3a%2294a85ac0-c175-491f-b669-b268223a2462%22%7d

In photoactive proteins the coupling between chromophore and protein matrix is exquisitely tuned, enabling optimal photosynthesis and photosensing. Proton transfer reactions may mediate this coupling, such as in proton-coupled electron transfer and excited state proton transfer.1–4 More reaction mechanisms likely exist,5 not least related to coherences,6 but remain to be demonstrated. Our work presents the crystallographic snapshots of the first 3 ps after photoactivation of the phytochrome from Deinococcus radiodurans. In excellent agreement with recent quantum chemical predictions, we reveal a detailed trajectory of the rotation of the chromophore D-ring by a spaceconserving mechanism. Intriguingly, we observe ultrafast rearrangement of a conserved hydrogen bond network close to the chromophore. Aided by molecular modelling and independently supported by femtosecond infrared spectroscopy, we assign these changes to an ultrafast proton transfer reaction of a conserved histidine. Contrasting established mechanisms,1–3 the protonation reaction occurs remotely from the photoexcited chromophore. Remote-controlled proton transfer is a new mechanism to couple the chromophore to the protein matrix. Occurring on the ultrafast time scale of coherent vibrational responses, we suggest that it may be widely used to transduce cofactor signals to their hosting enzymes.

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2. Demchenko, A. P. BBA Advances 3, 100085 (2023).

3. Migliore, A., Polizzi, N. F., Therien, M. J. & Beratan, D. N. Chem Rev 114, 3381–3465 (2014).

4. Parada, G. A. et al. Science 364, (2019).

5. Wang, H. et al. Science 316, 747–750 (2007).

6. Scholes, G. D. et al. Nature vol. 543 (2017).