The fraction of chains, or subunits, in a membrane protein structure (both monomers and multi-subunit complexes) that are membrane-embedded. Coloring indicates the relative contribution of membrane-spanning subunits or chains in the complex to which each chain belongs. Thus, the first column shows that among all the entries containing just one membrane-spanning subunit or chain, the vast majority are monomers (gray), and there are smaller percentages of dimers (yellow), trimers (orange), tetramers (dark orange), or higher oligomers (red) with a single membrane-spanning chain.
