Maltose O-acyltransferase (MAT)-like: This family is composed of maltose O-acetyltransferase, galactoside O-acetyltransferase (GAT), xenobiotic acyltransferase (XAT) and similar proteins. MAT and GAT catalyze the CoA-dependent acetylation of the 6-hydroxyl group of their respective sugar substrates. MAT acetylates maltose and glucose exclusively while GAT specifically acetylates galactopyranosides. XAT catalyzes the CoA-dependent acetylation of a variety of hydroxyl-bearing acceptors such as chloramphenicol and streptogramin, among others. XATs are implicated in inactivating xenobiotics leading to xenobiotic resistance in patients. Members of this family contain a a left-handed parallel beta-helix (LbH) domain with at least 5 turns, each containing three imperfect tandem repeats of a hexapeptide repeat motif (X-[STAV]-X-[LIV]-[GAED]-X). They are trimeric in their active form.
Comment:Based on the structures of E. coli galactoside acetyltransferase and Enterococcus faecium streptogramin acetyltransferase Vat(D) bound to CoA and their respective substrates.
Comment:Active acetyltransferases in this family are trimeric, with active sites located at the interface between two LbH subunits. The trimer structure contains three active sites and each subunit contributes to two active sites via residues located on two surfaces.
Structure:1KRV; E. coli Galactoside Acetyltransferase trimer binds three CoA and substrate 4-nitrophenylgalactoside molecules; defined at 4A contacts. - View structure with Cn3D
Structure:1KHR_A; Enterococcus faecium streptogramin acetyltransferase Vat(D) binds CoA and substrate Virginiamycin; defined at 4A contacts. Shown are two active sites within the trimer. - View structure with Cn3D