Source:http://linkedlifedata.com/resource/umls/id/C1523025
GO: Interacting selectively and non-covalently with a quaternary ammonium group, including glycine betaine, choline, carnitine and proline. A quaternary ammonium group is any compound that can be regarded as derived from ammonium hydroxide or an ammonium salt by replacement of all four hydrogen atoms of the NH4+ ion by organic groups. [GOC:ai]