2POR is a transmembrane protein called a porin. Porins are generic barrel shaped proteins that let non-specific polar molecules with molecular weights less than 600 daltons pass through cell membranes. This porin, 2POR, is from the bacteria Rhodobacter capsulatus.

The barrel of 2POR consists of 16 beta strands. The quaternary structure of the molecules is a trimer. The structure of 2POR to 1.8 angstroms was determined in 1992 by Weiss and Schulz using XRay crystallography.

This cartoon display of 2POR illustrates the secondary structure. This picture is taken looking down the barrel shape of the protein. The yellow structures are anti-parellel sheets which form a barrel. The pink structures are alpha-helices, which line the barrel.