Porins are channel proteins in the outer membrane of gram negative bacteria which mediate the uptake of molecules required for growth and survival. Escherichia coli OmpG forms a 14 stranded beta-barrel and in contrast to most porins, appears to function as a monomer [1]. The central pore of OmpG is wider than other E. coli porins and it is speculated that it may form a non-specific channel for the transport of larger oligosaccharides [1].

1: Crystal structure of the monomeric porin OmpG. Subbarao GV, van den Berg B; J Mol Biol. 2006;360:750-759. PMID:16797588