Steven L Roderick — Page 2

PubMed2002

Aminoglycoside 2'-N-acetyltransferase from Mycobacterium tuberculosis in complex with coenzyme A and aminoglycoside substrates.

AAC(2')-Ic catalyzes the coenzyme A (CoA)-dependent acetylation of the 2' hydroxyl or amino group of a broad spectrum of aminoglycosides. The crystal structure of the AAC(2')-Ic from Mycobacterium tuberculosis has been determined in the apo enzyme form and in ternary complexes with CoA and either tobramycin, kanamycin A or ribostamycin, representing the first structures of an aminoglycoside acetyltransferase bound to a drug. The overall fold of AAC(2')-Ic places it in the GCN5-related N-acetyltransferase (GNAT) superfamily. Although the physiological function of AAC(2')-Ic is uncertain, a structural analysis of these high-affinity aminoglycoside complexes suggests that the enzyme may acetylate a key biosynthetic intermediate of mycothiol, the major reducing agent in mycobacteria, and participate in the regulation of cellular redox potential.

Acetyltransferases↗

PubMed2002

Acyl group specificity at the active site of tetrahydridipicolinate N-succinyltransferase.

Tetrahydrodipicolinate N-succinyltransferase (DapD) catalyzes the succinyl-CoA-dependent acylation of L-2-amino-6-oxopimelate to 2-N-succinyl-6-oxopimelate as part of the succinylase branch of the meso-diaminopimelate/lysine biosynthetic pathway of bacteria, blue-green algae, and plants. This pathway provides meso-diaminopimelate as a building block for cell wall peptidoglycan in most bacteria, and is regarded as a target pathway for antibacterial agents. We have solved the X-ray crystal structures of DapD in ternary complexes with pimelate/succinyl-CoA and L-2-aminopimelate with the nonreactive cofactor analog, succinamide-CoA. These structures define the binding conformation of the cofactor succinyl group and its interactions with the enzyme and place its thioester carbonyl carbon in close proximity to the nucleophilic 2-amino group of the acceptor, in support of a direct attack ternary complex mechanism. The acyl group specificity differences between homologous tetrahydrodipicolinate N-acetyl- and N-succinyltransferases can be rationalized with reference to at least three amino acids that interact with or give accessible active site volume to the cofactor succinyl group. These residues account at least in part for the substrate specificity that commits metabolic intermediates to either the succinylase or acetylase branches of the meso-diaminopimelate/lysine biosynthetic pathway.

Acyl Coenzyme A↗