Anhui Province Key Laboratory of Active Biological Macro-molecules, Wannan Medical College, Wuhu, Anhui 241002, China.
College of Life Sciences, Anhui Normal University, Wuhu, Anhui 241000, China.
Nucleic Acids Res. 2022 Jun 10;50(10):5757-5771. doi: 10.1093/nar/gkac416.
Synechococcus elongatus, formerly known as Anacystis nidulans, is a representative species of cyanobacteria. It is also a model organism for the study of photoreactivation, which can be fully photoreactivated even after receiving high UV doses. However, for a long time, only one photolyase was found in S. elongatus that is only able to photorepair UV induced cyclobutane pyrimidine dimers (CPDs) in DNA. Here, we characterize another photolyase in S. elongatus, which belongs to iron-sulfur bacterial cryptochromes and photolyases (FeS-BCP), a subtype of prokaryotic 6-4 photolyases. This photolyase was named SePhrB that could efficiently photorepair 6-4 photoproducts in DNA. Chemical analyses revealed that SePhrB contains a catalytic FAD cofactor and an iron-sulfur cluster. All of previously reported FeS-BCPs contain 6,7-dimethyl-8-ribityllumazine (DMRL) as their antenna chromophores. Here, we first demonstrated that SePhrB possesses 7,8-didemethyl-8-hydroxy-5-deazariboflavin (8-HDF) as an antenna chromophore. Nevertheless, SePhrB could be photoreduced without external electron donors. After being photoreduced, the reduced FAD cofactor in SePhrB was extremely stable against air oxidation. These results suggest that FeS-BCPs are more diverse than expected which deserve further investigation.
聚球藻（Synechococcus elongatus），以前被称为鱼腥藻（Anacystis nidulans），是蓝细菌的代表物种。它也是光复活研究的模式生物，即使在接受高剂量的紫外线后，也可以完全进行光复活。然而，在很长一段时间里，人们只在聚球藻中发现了一种光解酶，它只能修复 DNA 中由紫外线引起的环丁烷嘧啶二聚体（CPDs）。在这里，我们描述了聚球藻中的另一种光解酶，它属于铁硫细菌隐色体和光解酶（FeS-BCP），这是一种原核 6-4 光解酶的亚型。这种光解酶被命名为 SePhrB，它可以有效地修复 DNA 中的 6-4 光产物。化学分析表明，SePhrB 含有一个催化黄素腺嘌呤二核苷酸（FAD）辅因子和一个铁硫簇。所有以前报道的 FeS-BCP 都含有 6,7-二甲基-8-核糖基黄素（DMRL）作为它们的天线发色团。在这里，我们首次证明了 SePhrB 具有 7,8-二去甲基-8-羟基-5-去氮核糖黄素（8-HDF）作为天线发色团。然而，SePhrB 可以在没有外部电子供体的情况下进行光还原。光还原后，SePhrB 中的还原 FAD 辅因子对空气氧化非常稳定。这些结果表明，FeS-BCP 比预期的更为多样化，值得进一步研究。
