TY - JOUR T1 - Structural characterization of encapsulated ferritin provides insight into iron storage in bacterial nanocompartments JF - bioRxiv DO - 10.1101/063495 SP - 063495 AU - Didi He AU - Sam Hughes AU - Sally Vanden-Hehir AU - Atanas Georgiev AU - Kirsten Altenbach AU - Emma Tarrant AU - C. Logan Mackay AU - Kevin J. Waldron AU - David J. Clarke AU - Jon Marles-Wright Y1 - 2016/01/01 UR - http://biorxiv.org/content/early/2016/07/12/063495.abstract N2 - Ferritins are ubiquitous proteins that oxidise and store iron within a protein shell to protect cells from oxidative damage. We have characterized the structure and function of a new member of the ferritin superfamily that is sequestered within an encapsulin capsid. We show that this encapsulated ferritin (EncFtn) has two main alpha helices, which assemble in a metal dependent manner to form a ferroxidase centre at a dimer interface. EncFtn adopts an open decameric structure that is topologically distinct from other ferritins. While EncFtn acts as a ferroxidase, it cannot mineralize iron. Conversely, the encapsulin shell associates with iron, but is not enzymatically active, and we demonstrate that EncFtn must be housed within the encapsulin for iron storage. This encapsulin nanocompartment is widely distributed in bacteria and archaea and represents a distinct class of iron storage system where the oxidation and mineralization of iron are distributed between two proteins. ER -