1.I.3. The Bacterial (Planctomycetes) Nuclear Pore-like Complex (B-NPC) Family
Planctomycetes are distinguished from other Bacteria by compartmentalization of cells via internal membranes. The planctomycete Gemmata obscuriglobus contains a nuclear body-like compartment, and thus possesses a type of cell organization with parallels to the eukaryote nucleus. Sagulenko et al. 2017 showed that pore-like structures occur in internal membranes of G.obscuriglobus and that they have elements structurally similar to those of eukaryote nuclear pores, including a basket, ring-spoke structure, and eight-fold rotational symmetry. Bioinformatic analysis of proteomic data revealed that some of the G. obscuriglobus proteins associated with pore-containing membranes possess structural domains found in eukaryote nuclear pore complexes. Moreover, immunogold labelling demonstrates localization of one such protein, containing a β-propeller domain, specifically to the G. obscuriglobus pore-like structures. Finding bacterial pores within internal cell membranes and with structural similarities to eukaryote nuclear pore complexes raises the dual possibilities of either hitherto undetected homology or stunning evolutionary convergence (Sagulenko et al. 2017).