Nucleotidyltransferase domain. Members of this family belong to a large family of nucleotidyltransferases. This family includes kanamycin nucleotidyltransferase (KNTase) which is a plasmid-coded enzyme responsible for some types of bacterial resistance to aminoglycosides. KNTase in-activates antibiotics by catalyzing the addition of a nucleotidyl group onto the drug.