has participant toxin export channel activity http://purl.obolibrary.org/obo/go.owl Enables the energy independent passage of toxins, sized less than 1000 Da, across a membrane towards the outside of the cell. The transmembrane portions of porins consist exclusively of beta-strands which form a beta-barrel. They are found in the outer membranes of Gram-negative bacteria, mitochondria, plastids and possibly acid-fast Gram-positive bacteria. porin activity toxin transmembrane transporter activity toxin