Institute of Organic Chemistry and Chemical Biology, Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany.
Institute for Technical Microbiology, Faculty for Biotechnology, Mannheim University of Applied Sciences, 68163 Mannheim, Germany.
Microbiology (Reading). 2019 Oct;165(10):1095-1106. doi: 10.1099/mic.0.000835.
Dodecins are small flavin-binding proteins that are widespread amongst haloarchaeal and bacterial species. Haloarchaeal dodecins predominantly bind riboflavin, while bacterial dodecins have been reported to bind riboflavin-5'-phosphate, also called flavin mononucleotide (FMN), and the FMN derivative, flavin adenine dinucleotide (FAD). Dodecins form dodecameric complexes and represent buffer systems for cytoplasmic flavins. In this study, dodecins of the bacteria (SdDod) and (ScDod) were investigated. Both dodecins showed an unprecedented low affinity for riboflavin, FMN and FAD when compared to other bacterial dodecins. Significant binding of FMN and FAD occurred at relatively low temperatures and under acidic conditions. X-ray diffraction analyses of SdDod and ScDod revealed that the structures of both dodecins are highly similar, which explains their similar binding properties for FMN and FAD. In contrast, SdDod and ScDod showed very different properties with regard to the stability of their dodecameric complexes. Site-directed mutagenesis experiments revealed that a specific salt bridge (D10-K62) is responsible for this difference in stability.
十二聚体是广泛存在于盐杆菌和细菌物种中的小型黄素结合蛋白。盐杆菌十二聚体主要结合核黄素，而细菌十二聚体已被报道结合核黄素-5'-磷酸，也称为黄素单核苷酸 (FMN)，以及 FMN 衍生物黄素腺嘌呤二核苷酸 (FAD)。十二聚体形成十二聚体复合物，是细胞质黄素的缓冲系统。在这项研究中，研究了细菌 （SdDod） 和 （ScDod） 的十二聚体。与其他细菌十二聚体相比，这两种十二聚体对核黄素、FMN 和 FAD 的亲和力都非常低。FMN 和 FAD 的显著结合发生在相对较低的温度和酸性条件下。SdDod 和 ScDod 的 X 射线衍射分析表明，这两种十二聚体的结构高度相似，这解释了它们对 FMN 和 FAD 的相似结合特性。相比之下，SdDod 和 ScDod 在其十二聚体复合物的稳定性方面表现出非常不同的性质。定点突变实验表明，特定的盐桥 (D10-K62) 是导致这种稳定性差异的原因。
