The COOH terminus of arylamine N-acetyltransferase from Salmonella typhimurium controls enzymic activity.
Arylamine N-acetyltransferases (NATs) are a homologous family of enzymes, which acetylate arylamines, arylhydroxylamines, and arylhydrazines by acetyl transfer from acetyl-coenzyme A (Ac-CoA) and are found in many organisms. NAT was first identified as the enzyme responsible for the inactivation of the anti-tubercular drug isoniazid in humans. The three-dimensional structure of NAT from Salmonella typhimurium has been resolved and shown to have three distinct domains and an active site catalytic triad composed of "Cys(69)-His(107)-Asp(122)," which is typical of hydrolytic enzymes such as the cysteine proteases. The crystal unit cell consists of a dimer of tetramers, with the C terminus of individual monomers juxtaposed. To investigate the function of the first two domains of full-length NAT from S. typhimurium and to investigate the role of the C terminus of NAT, truncation mutants were made with either the C-terminal undecapeptide or the entire third domain (85 amino acids) missing. Unlike the full-length NAT protein (281 amino acids), the truncation mutants of NAT from S. typhimurium are toxic when overexpressed intracellularly in Escherichia coli. Full-length NAT hydrolyses Ac-CoA but only in the presence of an arylamine substrate. Both truncation mutants, however, hydrolyze Ac-CoA even in the absence of arylamine substrate, illustrating that the C-terminal undecapeptide controls hydrolysis of Ac-CoA by NAT from S. typhimurium.
Mushtaq
Adeel
A
Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, United Kingdom. adeel.mushtaq@pharm.ox.ac.uk
Payton
Mark
M
Sim
Edith
E
D000588:Amines / Q000378:metabolism; D000595:Amino Acid Sequence; D001191:Arylamine N-Acetyltransferase / Q000737:chemistry*; D001665:Binding Sites; D002384:Catalysis; D003001:Cloning, Molecular; D003600:Cytosol / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D012486:Salmonella typhimurium / Q000201:enzymology*
D000588:Amines; D011994:Recombinant Proteins; D001191:Arylamine N-Acetyltransferase