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bioRxiv · 10.1101/2021.03.16.435614

Structure of SOQ1 lumenal domains identifies potential disulfide exchange for negative regulation of photoprotection, qH

Yu, G.·Pan, X.·Hao, J.·Shi, L.·Zhang, Y.·Wang, J.·Xiao, Y.·Yang, F.·Lou, J.·Chang, W.·Malnoe, A.·Li, M.
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Abstract

Non-photochemical quenching (NPQ) plays an important role for phototrophs in decreasing photo-oxidative damage. qH is a sustained component of NPQ and depends on the plastid lipocalin (LCNP). A thylakoid membrane-anchored protein SUPPRESSOR OF QUENCHING1 (SOQ1) prevents qH formation by inhibiting LCNP. SOQ1 suppresses qH with its lumen-located C-terminal Trx-like and NHL domains. Here we report crystal structures and biochemical characterization of SOQ1 lumenal domains. Our results show that the Trx-like and NHL domains are stably associated, with the potential redox-active motif located at their interface. Residue E859 essential for SOQ1 function is pivotal for mediating the inter-domain interaction. Moreover, the C-terminal region of SOQ1 forms an independent {beta}-stranded domain, which possibly interacts with the Trx-like domain through disulfide exchange. Furthermore, SOQ1 is susceptible to cleavage at the loops connecting the neighboring domains both in vitro and in vivo, which could be a regulatory process for its suppression function of qH.

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Yu, G., Pan, X., Hao, J., Shi, L., Zhang, Y., Wang, J., Xiao, Y., Yang, F., Lou, J., Chang, W., Malnoe, A., Li, M.. 2021-03-17. Structure of SOQ1 lumenal domains identifies potential disulfide exchange for negative regulation of photoprotection, qH. https://doi.org/10.1101/2021.03.16.435614

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