Instituto de Ciencias del Mar y Limnología, Unidad Académica de Sistemas Arrecifales, Universidad Nacional Autónoma de México-UNAM, Prol. Avenida Niños Héroes S/N, 77580 Puerto Morelos, Q ROO, Mexico.
Photosynth Res. 2013 Jul;115(2-3):167-78. doi: 10.1007/s11120-013-9856-8. Epub 2013 May 25.
A photosystem II component, the PsbO protein is essential for maximum rates of oxygen production during photosynthesis, and has been extensively characterized in plants and cyanobacteria but not in symbiotic dinoflagellates. Its close interaction with D1 protein has important environmental implications since D1 has been identified as the primary site of damage in endosymbiotic dinoflagellates after thermal stress. We identified and biochemically characterized the PsbO homolog from Symbiodinium kawagutii as a 28-kDa protein, and immunolocalized it to chloroplast membranes. Chloroplast association was further confirmed by western blot on photosynthetic membrane preparations. TX-114 phase partitioning, chromatography, and SDS-PAGE for single band separation and partial peptide sequencing yielded peptides identical or with high identity to PsbO from dinoflagellates. Analysis of a cDNA library revealed three genes differing by only one aminoacid residue in the in silico-translated ORFs despite greater differences at nucleotide level in the untranslated, putative regulatory sequences. The consensus full amino acid sequence displayed all the characteristic domains and features of PsbO from other sources, but changes in functionally critical, highly conserved motifs were detected. Our biochemical, molecular, and immunolocalization data led to the conclusion that the 28-kDa protein from S. kawagutii is the PsbO homolog, thereby named SkPsbO. We discuss the implications of critical amino acid substitutions for a putative regulatory role of this protein.
一种光系统 II 组份，PsbO 蛋白对于光合作用中氧气最大产生速率是必不可少的，它在植物和蓝藻中得到了广泛的研究，但在共生甲藻中却没有。它与 D1 蛋白的密切相互作用具有重要的环境意义，因为 D1 已被确定为热应激后内共生甲藻中主要的损伤部位。我们从共生甲藻 Symbiodinium kawagutii 中鉴定并生化表征了 PsbO 同源物，它是一种 28kDa 的蛋白，并将其免疫定位到叶绿体膜上。叶绿体的关联通过光合膜制剂的 Western blot 进一步得到证实。TX-114 相分离、色谱和 SDS-PAGE 用于单带分离和部分肽测序，得到的肽与来自甲藻的 PsbO 相同或具有高度同源性。cDNA 文库的分析显示，尽管在未翻译的、假定的调节序列中核苷酸水平存在更大差异，但在计算机翻译的 ORFs 中仅相差一个氨基酸残基的三个基因。共识全长氨基酸序列显示了所有来自其他来源的 PsbO 的特征结构域和特征，但在功能关键的高度保守基序中检测到了变化。我们的生化、分子和免疫定位数据得出的结论是，来自 S. kawagutii 的 28kDa 蛋白是 PsbO 同源物，因此命名为 SkPsbO。我们讨论了这些关键氨基酸取代对该蛋白的假定调节作用的影响。
