Bieger Boris, Essen Lars-Oliver, Oesterhelt Dieter
Department of Membrane Biochemistry, Max Planck Institute for Biochemistry, Am Klopferspitz 18a, D-82152, Martinsried, Germany.
Structure. 2003 Apr;11(4):375-85. doi: 10.1016/s0969-2126(03)00048-0.
A novel, 68 amino acid long flavoprotein called dodecin has been discovered in the proteome of Halobacterium salinarum by inverse structural genomics. The 1.7 A crystal structure of this protein shows a dodecameric, hollow sphere-like arrangement of the protein subunits. Unlike other known flavoproteins, which bind only monomeric flavin cofactors, the structure of the dodecin oligomer comprises six riboflavin dimers. The dimerization of these riboflavins along the re-faces is mediated by aromatic, antiparallel pi staggering of their isoalloxazine moieties. A unique aromatic tetrade is formed by further sandwiching of the riboflavin dimers between the indole groups of two symmetry-related Trp36s. So far, the dodecins represent the smallest known flavoproteins. Based on the structure and the wide spread occurrences in pathogenic and soil eubacteria, a function in flavin storage or protection against radical or oxygenic stress is suggested for the dodecins.
通过反向结构基因组学，在盐生盐杆菌的蛋白质组中发现了一种名为十二菌素的新型黄素蛋白，其长度为68个氨基酸。该蛋白质的1.7埃晶体结构显示，蛋白质亚基呈十二聚体、空心球状排列。与其他仅结合单体黄素辅因子的已知黄素蛋白不同，十二菌素寡聚体的结构包含六个核黄素二聚体。这些核黄素沿再面的二聚化是由其异咯嗪部分的芳香族反平行π交错介导的。通过将核黄素二聚体进一步夹在两个对称相关的Trp36的吲哚基团之间，形成了一个独特的芳香十四聚体。到目前为止，十二菌素是已知最小的黄素蛋白。基于其结构以及在致病和土壤真细菌中的广泛存在，推测十二菌素具有黄素储存功能或具有抵抗自由基或氧化应激的作用。
