This domain is found at the C-terminal end of Aminoglycoside adenylyltransferase from Salmonella typhimurium (AadA) and other proteins associated with methicillin-resistant bacteria. AadA adenylates the 3''-hydroxyl group of the streptomycin glucosamine ring and the 9-hydroxyl group of the spectinomycin actinamine ring, mediating bacterial resistance to these antibiotics. This enzyme is organised into two domains: a N-terminal domain with a nucleotidyltransferase fold (Pfam:PF01909) and a C-terminal domain (this entry) which consists of five alpha-helices forming an up-and-down alpha-helical bundle. This domain undergoes small conformational changes upon binding of ATP and magnesium that play a key role in the binding of the antibiotic compounds [1,2].

1: Structure of AadA from Salmonella enterica: a monomeric aminoglycoside (3'')(9) adenyltransferase. Chen Y, Nasvall J, Wu S, Andersson DI, Selmer M; Acta Crystallogr D Biol Crystallogr. 2015;71:2267-2277. PMID:26527143

2: Structural mechanism of AadA, a dual-specificity aminoglycoside adenylyltransferase from Salmonella enterica. Stern AL, Van der Verren SE, Kanchugal P S, Nasvall J, Gutierrez-de-Teran H, Selmer M; J Biol Chem. 2018;293:11481-11490. PMID:29871922