Photochemical Reactions of the LOV and LOV-Linker Domains of the Blue Light Sensor Protein YtvA

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• 作者：Seokwoo Choi ; Yusuke Nakasone ; Klaas J. Hellingwerf ; Masahide Terazima
• 刊名：Biochemistry
• 出版年：2016
• 出版时间：June 7, 2016
• 年：2016
• 卷：55
• 期：22
• 页码：3107-3115
• 全文大小：486K
• 年卷期：0
• ISSN：1520-4995

文摘

YtvA is a blue light sensor protein composed of an N-terminal LOV (light–oxygen–voltage) domain, a linker helix, and the C-terminal sulfate transporter and anti-σ factor antagonist domain. YtvA is believed to act as a positive regulator for light and salt stress responses by regulating the σ_B transcription factor. Although its biological function has been studied, the reaction dynamics and molecular mechanism underlying the function are not well understood. To improve our understanding of the signaling mechanism, we studied the reaction of the LOV domain (YLOV, amino acids 26–127), the LOV domain with its N-terminal extension (N-YLOV, amino acids 1–127), the LOV domain with its C-terminal linker helix (YLOV-linker, amino acids 26–147), and the YLOV domain with the N-terminal extension and the C-terminal linker helix (N-YLOV-linker, amino acids 1–147) using the transient grating method. The signals of all constructs showed adduct formation, thermal diffusion, and molecular diffusion. YLOV showed no change in the diffusion coefficient (D), while the other three constructs showed a significant decrease in D within ∼70 μs of photoexcitation. This indicates that conformational changes in both the N- and C-terminal helices of the YLOV domain indeed do occur. The time constant in the YtvA derivatives was much faster than the corresponding dynamics of phototropins. Interestingly, an additional reaction was observed as a volume expansion as well as a slight increase in D only when both helices were included. These findings suggest that although the rearrangement of the N- and C-terminal helices occurs independently on the fast time scale, this change induces an additional conformational change only when both helices are present.