TCDB is operated by the Saier Lab Bioinformatics Group

Cyanobacterial septa (also called microplasmodesmata) between vegetative cells and between vegetative cells and N2-fixing heterocysts that appear to include at least 3 proteins:  SepJ, which is a member of the DMT superfamily (2.A.7.3.81) and seems to transport acidic amino acids and other hydrophilic amino acids, as well as FraC, and FraD which seem to be cyanobacterium-specific (Nürnberg et al. 2015). FraC and FraD each have 4 or 5 and 5 TMSs, respectively, and are encoded in a single operon, fraCDE. The septa have a mean diameter of about 7 - 8 nm with varying numbers of nanopores (holes in the peptidoglycan) (Flores et al. 2018). Each septa has a cap and a cyanophycin plug as well as a cytoplasmic membrane-achored tube crossing the intercellular space between cells. The AmiC amidase may drill holes in the peptidoglycan druing septal biogenesis to generate the nanopores. The septa can transport a variety of sugars, amino acids, peptides and 5-carboxyflorescein. Proteins that affect nanopore formation include the product of the alr3353 gene (SjcF1; 760 aas; a peptidoglycan binding protein LytM-like factor) which is homologous to B. subtilis proteins in gap junction-like structures (TC# 1.A.34.1.1-3) and the SpoIIA-SpoQ2 complex (TC# 9.B.70.1.1) (Flores et al. 2018).

The septum proteins, FraC, FraD and SepJ of Anabaena (Nostoc) sp. strain PCC 7120
FraC, 179 aas and 4 or 5 TMSs, P46078
FraD, 343 aas and 5 TMSs, P46079
SepJ, see 2.A.7.3.81

FraCD/SepJ with FraC of 172 aas with 4 TMSs, FraD of 193 aas with 5 TMSs, and SepJ (DUF6) of 566 aas with 10 C-terminal TMSs and a long N-terminal hydrophilic domain.

FraCD/SepJ of Arthrospira platensis (Spirulina platensis)

FraCD/SepJ; FraC, 194 aas with 4 or 5 TMSs; FraD, 180 aas with 4 TMSs; and SepJ, 431 aas with 10 TMSs. SepJ is a DMT superfamiy member.

FraCD/SepJ of Roseofilum reptotaenium
FraC, OJJ18935, 194 aas with 4 or 5 TMSs
FraD, OFF18936, 180 aas with 4 TMSs
SepJ, OJJ22670, 431 aas with 10 C-terminal TMSs