Marine Synechococcus are widespread in part because they are efficient at harvesting available light using their complex antenna, or phycobilisome, composed of multiple phycobiliproteins and bilin chromophores. Over 40% of Synechococcus strains are predicted to perform a type of chromatic acclimation that alters the ratio of two chromophores, green-light-absorbing phycoerythrobilin and blue-light-absorbing phycourobilin, to optimize light capture by phycoerythrin in the phycobilisome. Lyases are enzymes which catalyze the addition of bilin chromophores to specific cysteine residues on phycobiliproteins and are involved in chromatic acclimation. CpeY, a candidate lyase in the model strain Synechococcus sp. RS9916, added phycoerythrobilin to cysteine 82 of only the α subunit of phycoerythrin I (CpeA) in the presence or absence of the chaperone-like protein CpeZ in a recombinant protein expression system. These studies demonstrated that recombinant CpeY attaches phycoerythrobilin to as much as 72% of CpeA, making it one of the most efficient phycoerythrin lyases characterized to date. Phycobilisomes from a cpeY- mutant showed a near native bilin composition in all light conditions except for a slight replacement of phycoerythrobilin by phycourobilin at CpeA cysteine 82. This demonstrates that CpeY is not involved in any chromatic acclimation-driven chromophore changes and suggests that the chromophore attached at cysteine 82 of CpeA in the cpeY- mutant is ligated by an alternative phycoerythrobilin lyase. Although loss of CpeY does not greatly inhibit native phycobilisome assembly in vivo, the highly active recombinant CpeY can be used to generate large amounts of fluorescent CpeA for biotechnological uses.

中文翻译：

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CpeY是海洋红球菌中藻红蛋白Iα亚基的半胱氨酸82的藻红蛋白裂解酶。

海洋Synechococcus之所以广泛使用，部分是因为它们能够有效地利用由多种藻胆蛋白和Bilin生色团组成的复杂天线或藻胆体来收集可用光。预计超过40％的Synechococcus菌株会执行一种色适应性，从而改变两种发色团（吸收绿光的藻红蛋白和吸收蓝光的藻红蛋白）的比率，以优化藻红蛋白在藻胆体中捕获的光。裂合酶是催化将胆红蛋白生色团加到藻胆蛋白上的特定半胱氨酸残基上的酶，并参与颜色适应。CpeY，模型菌株Synechococcus sp。中的候选裂解酶。RS9916，在重组蛋白表达系统中，在存在或不存在伴侣蛋白样蛋白CpeZ的情况下，仅在藻红蛋白I（CpeA）的α亚基的半胱氨酸82中添加藻红蛋白。这些研究表明，重组CpeY使藻红蛋白结合至多达72％的CpeA，使其成为迄今表征的最有效的藻红蛋白裂解酶之一。来自cpeY突变体的藻胆体在所有光照条件下均表现出接近天然的胆红素组成，除了在CpeA半胱氨酸82上被藻尿胆素轻微替代了藻红蛋白外。这表明CpeY不参与任何由色适应驱动的生色团变化，并暗示了生色团连接在cpeY-突变体中CpeA的半胱氨酸82上的肽被另一种藻红蛋白裂解酶连接。