5da5
Crystal structure of Rhodospirillum rubrum Rru_A0973
Structural highlights
FunctionFER_RHORT Cargo protein of a type 1 encapsulin nanocompartment. A ferritin-like ferroxidase that mineralizes iron inside the encapsulin nanocompartment. Converts Fe(2+) to Fe(3+) that is released to the exterior of the decameric complex for deposition in the encapsulin nanocompartment. In solution the decamer binds 10-15 iron cations; in the encapsulin nanocompartment the decamer can bind up to 48 ions, perhaps via its internal channel and on its exterior. The empty encapsulin nanocompartment sequesters about 2200 Fe ions while the cargo-loaded nanocompartment can maximally sequester about 4150 Fe ions. EncFtn retains ferroxidase activity when encapsulated (PubMed:27529188). Flux in the active site di-iron metal center is thought to be controlled by the 'entry site' of the protein, which both attracts metal and controls the rate of iron oxidation (Probable). Encapsulation in the nanocompartment does not alter either function of this protein (PubMed:32878987).[1] [2] [3] Publication Abstract from PubMedFerritins 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 center 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. Structural characterization of encapsulated ferritin provides insight into iron storage in bacterial nanocompartments.,He D, Hughes S, Vanden-Hehir S, Georgiev A, Altenbach K, Tarrant E, Mackay CL, Waldron KJ, Clarke DJ, Marles-Wright J Elife. 2016 Aug 16;5. pii: e18972. doi: 10.7554/eLife.18972. PMID:27529188[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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