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).



Sagulenko, E., A. Nouwens, R.I. Webb, K. Green, B. Yee, G. Morgan, A. Leis, K.C. Lee, M.K. Butler, N. Chia, U.T. Pham, S. Lindgreen, R. Catchpole, A.M. Poole, and J.A. Fuerst. (2017). Nuclear Pore-Like Structures in a Compartmentalized Bacterium. PLoS One 12: e0169432.


TC#NameOrganismal TypeExample

The bacterial (Planctomycetes) Nuclear Pore-like Complex, B-NPC (Sagulenko et al. 2017). Several proteins were found to associate with the pore-containing membranes, and some were found to possess structural domains found in eukaryote nuclear pore complexes (Sagulenko et al. 2017).  Six proteins, shown to be associated with the B-NPC structure, are listed under this TC#.  They show sequence similarity with members of autotransport families 1 and 2 (TC#s 1.B.12 and 1.B.40) as well as members of a bacterial pore-forming toxin family (e.g., TC# 1.C.75). However these proteins have an unusual amino acid composition with lots of As, Gs, D, and Es, possibly (partially) accounting for the good scores.

B-NPC of Gemmata obscuriglobus
NPC-like protein of 1707 aas
NPC-like protein of 914 aas
NPC-like protein of 975 aas
NPC-like protein of 2559 aas
NPC-like protein of 436 aas
NPC-like protein of 704 aas