Firefly luciferase and fatty acyl-CoA synthetase are members of the acyl-CoA synthetase super family, which consists of a large N-terminal domain and a small C-terminal domain. Previously we found that firefly luciferase has fatty acyl-CoA synthetic activity, and also identified that the homolog of firefly luciferase in Drosophila melanogaster (CG6178) is a fatty acyl-CoA synthetase and is not a luciferase. In this study, we constructed chimeric proteins by exchanging the domain between Photinus pyralis luciferase (PpLase) and Drosophila CG6178, and determined luminescence and fatty acyl-CoA synthetic activities. A chimeric protein with the N-terminal domain of PpLase and the C-terminal domain of CG6178 (Pp/Dm) had luminescence activity, showing approximately 4% of the activity of wild-type luciferase. The Pp/Dm protein also had fatty acyl-CoA synthetic activity and the substrate specificity was similar to PpLase. In contrast, a chimeric protein with the N-terminal domain of CG6178 and the C-terminal of PpLase (Dm/Pp) had only fatty acyl-CoA synthetase activity, and the substrate specificity was similar to CG6178. These results suggest that the N-terminal domain of firefly luciferase is essential for substrate recognition, and that the C-terminal domain is indispensable but not specialized for the luminescence reaction.
萤火虫
荧光素酶和脂肪酰基-CoA合成酶是酰基-CoA合成酶超家族的成员,后者由一个大的N端结构域和一个小的C端结构域组成。此前我们发现萤火虫
荧光素酶具有脂肪酰-CoA合成活性,同时还发现黑腹果蝇中萤火虫
荧光素酶的同源物(CG6178)是脂肪酰-CoA合成酶,而不是
荧光素酶。在这项研究中,我们通过交换Photinus pyralis
荧光素酶(PpLase)和果蝇CG6178之间的结构域构建了嵌合蛋白,并测定了发光和脂肪酰-CoA合成活性。具有 PpLase N 端结构域和 CG6178 C 端结构域的嵌合蛋白(Pp/Dm)具有发光活性,其活性约为野生型
荧光素酶的 4%。Pp/Dm 蛋白还具有
脂肪酸酰-CoA 合成活性,其底物特异性与 PpLase 相似。相比之下,具有 CG6178 N 端结构域和 PpLase C 端结构域的嵌合蛋白(Dm/Pp)只有脂肪酰-CoA 合成酶活性,底物特异性与 CG6178 相似。这些结果表明,萤火虫
荧光素酶的 N 端结构域对于底物识别是必不可少的,而 C 端结构域对于发光反应是不可或缺的,但并不专一。