Involvement of Cys69 residue in the catalytic mechanism of N-hydroxyarylamine O-acetyltransferase of Salmonella typhimurium. Sequence similarity at the amino acid level suggests a common catalytic mechanism of acetyltransferase for S. typhimurium and higher organisms.
Acetyl-coenzyme A:N-hydroxyarylamine O-acetyltransferase is ubiquitous in species ranging from bacteria to mammals and is involved in the metabolic activation of N-hydroxyarylamines derived from mutagenic and carcinogenic aromatic amines and nitroarenes. The nucleotide sequence of the gene that encodes O-acetyltransferase of Salmonella typhimurium was determined, and its deduced amino acid sequence was compared with those of arylamine N-acetyltransferases (EC 2.3.1.5) of higher organisms. The gene of S. typhimurium encoded a protein with a calculated molecular weight of 32,177. Chromosome DNA of S. typhimurium TA1538/1,8-DNP, an O-acetyltransferase-deficient strain, had a -1 frameshift mutation of CCC to CC at the coding region. To date, 11 genes encoding N-acetyltransferase have been cloned from human, rabbit, hamster, and chicken. The N-terminal region of O-acetyltransferase of S. typhimurium with about 170 amino acids showed 25-33% homology with the corresponding region of N-acetyltransferase of the higher organisms. Of the 5 cysteine residues of O-acetyltransferase of S. typhimurium, Cys69 was the only residue that was conserved in all N-acetyltransferases of the higher organisms. The amino acid sequence of Arg-Gly-Gly-X-Cys, including the Cys69, was highly conserved. The mutant O-acetyltransferase of S. typhimurium, which contained Ala69 instead of Cys69, no longer showed the activities of O- and N-acetyltransferase. These results suggest that the Cys69 of S. typhimurium and its corresponding cysteine residues of the higher organisms are essential for the enzyme activities as acetyl-coenzyme A-binding sites.
Watanabe
M
M
Division of Genetics and Mutagenesis, National Institute of Hygienic Sciences, Tokyo, Japan.
Sofuni
T
T
Nohmi
T
T
D000105:Acetyl Coenzyme A / Q000378:metabolism; D000123:Acetyltransferases; D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D002384:Catalysis; D003545:Cysteine / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010957:Plasmids; D015183:Restriction Mapping; D012486:Salmonella typhimurium / Q000201:enzymology*; D012689:Sequence Homology, Nucleic Acid
D004269:DNA, Bacterial; D000105:Acetyl Coenzyme A; D000217:Acyltransferases; D000123:Acetyltransferases; C019736:N-hydroxyarylamine O-acetyltransferase; D003545:Cysteine