4PT2: Myxococcus Xanthus Encpasulin Protein (enca)

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.
PDB ID: 4PT2Download
MMDB ID: 121951
PDB Deposition Date: 2014/3/10
Updated in MMDB: 2014/09
Experimental Method:
electron microscopy
Resolution: 4.6  Å
Source Organism:
Similar Structures:
Biological Unit for 4PT2: 180-meric
Molecular Components in 4PT2
Label Count Molecule
Proteins (180 molecules)
Encapsulin Protein
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB