Type 1 encapsulin shell protein / Type 1 encapsulin shell protein / Encapsulating protein for peroxidase / encapsulin nanocompartment / peptidase activity / iron ion transport / intracellular iron ion homeostasis / defense response to bacterium / Type 1 encapsulin shell protein EncA
ジャーナル: EMBO J / 年: 2014 タイトル: A virus capsid-like nanocompartment that stores iron and protects bacteria from oxidative stress. 著者: Colleen A McHugh / Juan Fontana / Daniel Nemecek / Naiqian Cheng / Anastasia A Aksyuk / J Bernard Heymann / Dennis C Winkler / Alan S Lam / Joseph S Wall / Alasdair C Steven / Egbert Hoiczyk / 要旨: Living cells compartmentalize materials and enzymatic reactions to increase metabolic efficiency. While eukaryotes use membrane-bound organelles, bacteria and archaea rely primarily on protein-bound ...Living cells compartmentalize materials and enzymatic reactions to increase metabolic efficiency. While eukaryotes use membrane-bound organelles, bacteria and archaea rely primarily on protein-bound nanocompartments. Encapsulins constitute a class of nanocompartments widespread in bacteria and archaea whose functions have hitherto been unclear. Here, we characterize the encapsulin nanocompartment from Myxococcus xanthus, which consists of a shell protein (EncA, 32.5 kDa) and three internal proteins (EncB, 17 kDa; EncC, 13 kDa; EncD, 11 kDa). Using cryo-electron microscopy, we determined that EncA self-assembles into an icosahedral shell 32 nm in diameter (26 nm internal diameter), built from 180 subunits with the fold first observed in bacteriophage HK97 capsid. The internal proteins, of which EncB and EncC have ferritin-like domains, attach to its inner surface. Native nanocompartments have dense iron-rich cores. Functionally, they resemble ferritins, cage-like iron storage proteins, but with a massively greater capacity (~30,000 iron atoms versus ~3,000 in ferritin). Physiological data reveal that few nanocompartments are assembled during vegetative growth, but they increase fivefold upon starvation, protecting cells from oxidative stress through iron sequestration.
アルゴリズム: OTHER / 解像度のタイプ: BY AUTHOR / 解像度: 4.6 Å / 解像度の算出法: OTHER / ソフトウェア - 名称: bsoft 詳細: Final map was calculated dividing particles into two independent data sets 使用した粒子像数: 14000