This family consists of several bacterial proteins which are homologous to the oligogalacturonate-specific porin protein KdgM from Erwinia chrysanthemi. This phytopathogenic Gram-negative bacterium secretes pectinases, which are able to degrade the pectic polymers of plant cell walls and uses the degradation products as a carbon source for growth. KdgM is a Major Outer Membrane Protein (MOMP), whose synthesis is induced in the presence of the pectic derivatives. KdgM behaves like a voltage-dependent porin that is slightly selective for anions and that exhibits fast block in the presence of trigalacturonate. The family members seem to be monomeric, while the determined 3D structure of NanC porin suggests that they possess a 12-stranded ß-barrel, with rather short extracellular loops and a larger one that restricts the size of the pore. An outer membrane porin, KdgM, is indispensable for the uptake of acidic oligosaccharides. KdgM is folded into a regular 12-stranded antiparallel ß-barrel with a circular cross-section defining a transmembrane pore with a minimal radius of 3.1 Å.

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