Note that although at some level almost all cellular components can be thought of as protein complexes, this term is intended to exclude structures composed of the same repeating subunit or subunits, for example microtubules. Protein complexes encompassed by this term are generally not structural, and usually have a defined set of subunits.

protein-containing complex

GO:0032991

Any macromolecular complex composed of two or more polypeptide subunits, which may or may not be identical. Protein complexes may have other associated non-protein prosthetic groups, such as nucleotides, metal ions or carbohydrate groups.

protein-protein complex

cellular_component

GO:0032991