long-chain fatty acid transmembrane transporter activity porin activity long-chain fatty acid transporting porin activity https://github.com/geneontology/go-ontology/issues/26445 molecular_function GO:0015483 Enables the transfer of a long-chain fatty acid from one side of a membrane to the other. A long-chain fatty acid has an aliphatic tail containing 13 to 22 carbons. This transporter is a porin and so enables the energy independent passage of substances, sized less than 1000 Da, across a membrane. 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. TC:1.B.9.1.1 While there is not universal consensus on the lengths of short-, medium-, long- and very-long-chain fatty acids, the GO uses the definitions in ChEBI (see CHEBI:26666, CHEBI:59554, CHEBI:15904 and CHEBI:27283).