Direct Observation of Ultrafast Proton Rocking in the BLUF Domain. Issue 10 (20th January 2022)

• Record Type: Journal Article
• Authors: Kang, Xiu‐Wen; Chen, Zijing; Zhou, Zhongneng; Zhou, Yalin; Tang, Siwei; Zhang, Yifei; Zhang, Tianyi; Ding, Bei; Zhong, Dongping
• Is Part Of: Angewandte Chemie international edition. Volume 61:Issue 10(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-01-20
• Subjects: proton-coupled electron transfer -- proton rocking -- kinetic isotope effect -- photoreceptors -- ultrafast spectroscopy; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202114423
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: We present direct observation of ultrafast proton rocking in the central motif of a BLUF domain protein scaffold. The mutant design has taken consideration of modulating the proton‐coupled electron transfer (PCET) driving forces by replacing Tyr in the original motif with Trp, in order to remove the interference of a competing electron transfer pathway. Using femtosecond pump–probe spectroscopy and detailed kinetics analysis, we resolved an electron‐transfer‐coupled Grotthuss‐type forward and reverse proton rocking along the FMN–Gln–Trp proton relay chain. The rates of forward and reverse proton transfer are determined to be very close, namely 51 ps vs. 52 ps. The kinetic isotope effect (KIE) constants associated with the forward and reverse proton transfer are 3.9 and 5.3, respectively. The observation of ultrafast proton rocking is not only a crucial step towards revealing the nature of proton relay in the BLUF domain, but also provides a new paradigm of proton transfer in proteins for theoretical investigations. Abstract : Photoinduced proton‐coupled electron transfer processes of the OaPAC BLUF domain W mutant are uncovered to be forward sequential electron transfer and proton transfer followed by reverse sequential proton transfer and electron transfer mechanism. Significantly, the Grotthuss‐type proton rocking process is unambiguously resolved in this system and the associated kinetic isotope effect is measured.