Lipid astaxanthin, a potent antioxidant known as a natural sunscreen, accumulates in eukaryotic microalgae and confers photoprotection. We previously identified a photooxidative stress-inducible water-soluble astaxanthin-binding carotenoprotein (AstaP) in a eukaryotic microalga (Coelastrella astaxanthina Ki-4) isolated from an extreme environment. The distribution in eukaryotic microalgae remains unknown. Here we identified three novel AstaP orthologs in a eukaryotic microalga, Scenedesmus sp. Oki-4N. The purified proteins, named AstaP-orange2, AstaP-pink1, and AstaP-pink2, were identified as secreted fasciclin proteins with potent ¹O₂ quenching activity in aqueous solution, which are characteristics shared with Ki-4 AstaP. Nonetheless, the absence of glycosylation in the AstaP-pinks, the presence of a glycosylphosphatidylinositol (GPI) anchor motif in AstaP-orange2, and highly acidic isoelectric points (pI = 3.6–4.7), differed significantly from that of AstaP-orange1 (pI = 10.5). These results provide unique examples on the use of water-soluble forms of astaxanthin in photosynthetic organisms as novel strategies for protecting single cells against severe photooxidative stresses.

脂质虾青素是一种被称为天然防晒霜的有效抗氧化剂，在真核微藻中积累并赋予光保护作用。我们之前在从极端环境中分离出来的真核微藻（ Coelastrella astaxanthina Ki-4）中发现了一种光氧化应激诱导的水溶性虾青素结合胡萝卜素蛋白（AstaP）。真核微藻中的分布仍然未知。在这里，我们在真核微藻栅藻中鉴定了三种新的 AstaP 直向同源物。冲4N。纯化的蛋白被命名为 AstaP-orange2、AstaP-pink1 和 AstaP-pink2，被鉴定为分泌型成束蛋白，在水溶液中具有有效的¹ O ₂猝灭活性，这与 Ki-4 AstaP 具有相同的特征。尽管如此，AstaP-pinks 中不存在糖基化，AstaP-orange2 中存在糖基磷脂酰肌醇 (GPI) 锚定基序，以及高酸性等电点 (pI = 3.6–4.7)，与 AstaP-orange1 (pI) 显着不同。 = 10.5）。这些结果提供了在光合生物中使用水溶性虾青素作为保护单细胞免受严重光氧化应激的新策略的独特例子。