Harris Dvir, Wilson Adjele, Muzzopappa Fernando, Sluchanko Nikolai N, Friedrich Thomas, Maksimov Eugene G, Kirilovsky Diana, Adir Noam
Schulich Faculty of Chemistry, Technion, 3200003, Haifa, Israel.
Grand Technion Energy Program (GTEP), Technion, 3200003, Haifa, Israel.
Commun Biol. 2018 Aug 27;1:125. doi: 10.1038/s42003-018-0132-5. eCollection 2018.
A recently reported family of soluble cyanobacterial carotenoproteins, homologs of the C-terminal domain (CTDH) of the photoprotective Orange Carotenoid Protein, is suggested to mediate carotenoid transfer from the thylakoid membrane to the Helical Carotenoid Proteins, which are paralogs of the N-terminal domain of the OCP. Here we present the three-dimensional structure of a carotenoid-free CTDH variant from () PCC 7120. This CTDH contains a cysteine residue at position 103. Two dimer-forming interfaces were identified, one stabilized by a disulfide bond between monomers and the second between each monomer's β-sheets, both compatible with small-angle X-ray scattering data and likely representing intermediates of carotenoid transfer processes. The crystal structure revealed a major positional change of the C-terminal tail. Further mutational analysis revealed the importance of the C-terminal tail in both carotenoid uptake and delivery. These results have allowed us to suggest a detailed model for carotenoid transfer via these soluble proteins.
最近报道的一个可溶性蓝藻类胡萝卜素蛋白家族，是光保护橙色类胡萝卜素蛋白C端结构域（CTDH）的同源物，被认为介导类胡萝卜素从类囊体膜转移至螺旋类胡萝卜素蛋白，后者是OCP N端结构域的旁系同源物。在此，我们展示了来自集胞藻（Synechocystis）PCC 7120的无类胡萝卜素CTDH变体的三维结构。该CTDH在第103位含有一个半胱氨酸残基。鉴定出两个形成二聚体的界面，一个由单体间的二硫键稳定，另一个在每个单体的β折叠之间，二者均与小角X射线散射数据相符，且可能代表类胡萝卜素转移过程的中间体。晶体结构揭示了C端尾部的主要位置变化。进一步的突变分析揭示了C端尾部在类胡萝卜素摄取和传递中的重要性。这些结果使我们能够提出一个通过这些可溶性蛋白进行类胡萝卜素转移的详细模型。
