Nucleotidyltransferase (NT) domain of Staphylococcus aureus kanamycin nucleotidyltransferase, and similar proteins.
S. aureus KNTase is a plasmid encoded enzyme which confers resistance to a wide range of aminoglycoside antibiotics which have a 4'- or 4''-hydroxyl group in the equatorial position, such as kanamycin A. This enzyme transfers a nucleoside monophosphate group from a nucleotide (ATP,GTP, or UTP) to the 4'-hydroxyl group of kanamycin A. This enzyme is a homodimer, having two NT active sites. The nucleotide and antibiotic binding sites of each active site include residues from each monomer. Included in this subgroup is Escherichia coli AadA5 which confers resistance to the antibiotic spectinomycin and is a putative aminoglycoside-3'-adenylyltransferase. It is part of the aadA5 cassette of a class 1 integron. This subgroup also includes Haemophilus influenzae HI0073 which forms a 2:2 heterotetramer with an unrelated protein HI0074. Structurally HI0074 is related to the substrate-binding domain of S. aureus KNTase. The genes encoding HI0073 and HI0074 form an operon. Little is known about the substrate specificity or function of two-component NTs. The characterized members of this subgroup may not be representive of the function of this subgroup. This subgroup belongs to the Pol beta-like NT superfamily. In the majority of enzymes in this superfamily, two carboxylates, Dx[D/E], together with a third more distal carboxylate, co-ordinate two divalent metal cations involved in a two-metal ion mechanism of nucleotide addition. These carboxylate residues are conserved in this subgroup.
Comment:based on similarity to Staphylococcus aureus KNTase.
Structure:1KNY_A, Staphylococcus aureus KNTase homodimer, bound with Mg2+-AMP-CPP (an ATP analog) and kanamycin A, contacts determined at 4A.
Comment:Staphylococcus aureus KNTase is homodimeric, with two active sites in the dimer. Both monomers contribute residues to each NTP and antibiotic binding site. Other members of this group such as HI0073, the NT domain of HI0073/ HI0074 (a two-component NT), displays a different dimer association than that of Staphylococcus aureus KNTase.
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