Definition of a Protein Complex
A cellular component should include more than one gene product; complexes of one gene product with a cofactor, e.g. heme and chlorophyll, should not be included. Homomultimeric proteins, e.g. the homodimeric alcohol dehydrogenase, may be included as cellular component terms, as should heteromultimeric proteins, e.g. hemoglobin with alpha and beta chains.
All complexes in the component ontology should be given parentage under the general term protein complex ; GO:0043234.
To distinguish cellular components from functions, use 'complex' in the term name of a component, and append enzyme names with the word 'activity'. For example, the molecular function term pyruvate dehydrogenase activity ; GO:0004738 describes the enzyme activity whereas the cellular component term pyruvate dehydrogenase complex ; GO:0045254 describes the multi-subunit structure in which the enzyme activity resides.