Protein which contains at least one cysteine tryptophylquinone (CTQ) cross-link modification. CTQ is formed by oxidation of the indole ring of a tryptophan to form tryptophylquinone followed by covalent cross-linking with a cysteine residue. In the quinohemoprotein amine dehydrogenase, CTQ mediates during the catalytic cycle electron transfer from the substrate to either a copper protein, azurin, or cytochrome c-550.
