porin activity porin outer membrane exporter porin molecular_function Wikipedia:Porin_(protein) Reactome:R-HSA-9760573 Reactome:R-HSA-9926021 Enables the transfer of substances, sized less than 1000 Da, from one side of a membrane to the other. 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. Reactome:R-HSA-9911516 Reactome:R-HSA-9911510 Reactome:R-HSA-9914083 GO:0015288 wide pore channel activity