Unified Mechanism of Light-State BLUF Domain Photocycles by Capturing Proton Relay Intermediates

Yalin Zhou; Xiu-Wen Kang; Zhongneng Zhou; Zijing Chen; Shuhua Zou; Siwei Tang; Bingyao Wang; Kailin Wang; Dongping Zhong; Bei Ding

doi:10.34133/ultrafastscience.0072

Ultrafast Science (Jan 2024)

Unified Mechanism of Light-State BLUF Domain Photocycles by Capturing Proton Relay Intermediates

Yalin Zhou,
Xiu-Wen Kang,
Zhongneng Zhou,
Zijing Chen,
Shuhua Zou,
Siwei Tang,
Bingyao Wang,
Kailin Wang,
Dongping Zhong,
Bei Ding

Affiliations

Yalin Zhou: Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Xiu-Wen Kang: Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Zhongneng Zhou: Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Zijing Chen: Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Shuhua Zou: Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Siwei Tang: Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Bingyao Wang: Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Kailin Wang: Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Dongping Zhong: Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Bei Ding: Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.

DOI: https://doi.org/10.34133/ultrafastscience.0072
Journal volume & issue: Vol. 4

Abstract

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The blue light using flavin (BLUF) domain is one of nature’s smallest photoswitching protein domains, yet a cross-species photoactivation mechanism is lacking. Its photoactivation involves an intricate bidirectional proton-coupled electron transfer (PCET) reaction; however, the key reverse PCET route remains largely elusive, with its elementary steps undissected. Here, we resolved the light-state photoreaction cycles of the BLUF domains in 3 species, i.e., AppA from Rhodobacter sphaeroides, OaPAC from Oscillatoria acuminata, and SyPixD from Synechocystis sp. PCC6803, with a unified kinetic model. Using mutant design and femtosecond spectroscopy, we captured the spectroscopic snapshots of a key proton-relay intermediate in all species, revealing that the light-state photoreaction cycle consists of 4 elementary steps including a forward concerted electron-proton transfer (CEPT), a 2-step proton rocking, and a reverse CEPT. We emphasize that the last reverse CEPT step (1.5 to 3.7 ps) is shared by both the light-state and dark-state photocycles and is essential to the photoswitching functionality.

Published in Ultrafast Science

ISSN: 2765-8791 (Online)
Publisher: American Association for the Advancement of Science (AAAS)
Country of publisher: United States
LCC subjects: Science: Physics; Technology: Engineering (General). Civil engineering (General): Applied optics. Photonics
Website: https://spj.sciencemag.org/journals/ultrafastscience/

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