TY - JOUR T1 - Structure of SOQ1 lumenal domains identifies potential disulfide exchange for negative regulation of photoprotection, qH JF - bioRxiv DO - 10.1101/2021.03.16.435614 SP - 2021.03.16.435614 AU - Guimei Yu AU - Xiaowei Pan AU - Jingfang Hao AU - Lifang Shi AU - Yong Zhang AU - Jifeng Wang AU - Yang Xiao AU - Fuquan Yang AU - Jizhong Lou AU - Wenrui Chang AU - Alizée Malnoë AU - Mei Li Y1 - 2021/01/01 UR - http://biorxiv.org/content/early/2021/03/17/2021.03.16.435614.abstract N2 - 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 β-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.Competing Interest StatementThe authors have declared no competing interest. ER -