PDB ID or protein name


OPM consists of quaternary complexes (biological units) that are classified based on the structure of their main transmembrane or membrane-associated domain. The classification was built using SCOP and TCDB, but it differs from both systems in certain aspects. There are four levels of hierarchy in the classification:

  1. Type: transmembrane proteins, monotopic/peripheral proteins, or membrane-active peptides.
  2. Class: all-α, all-β, α+β, α/β, or nonregular proteins.
  3. Superfamily: evolutionarily related proteins with superimposable 3D structures.
  4. Family: proteins with detectable sequence homology.

OPM allows sorting of membrane proteins by hydrophobic thicknesses, tilt angles, destination membranes, number of transmembrane helices or subunits, structural family and superfamily, or biological source.