The conserved glycine/alanine residue of the active-site loop containing the putative acetylCoA-binding motif is essential for the overall structural integrity of Mesorhizobium loti arylamine N-acetyltransferase 1.
The arylamine N-acetyltransferases are important xenobiotic-metabolizing enzymes that catalyze an acetyl group transfer from acetylCoA to arylamine substrates. NAT enzymes possess an active-site loop (the active-site P-loop) involved in substrate binding and selectivity. The Gly/Ala residue present at the start of the active-site P-loop, although conserved in all NAT enzymes, is not involved in the catalytic mechanism or substrate binding. Here we show that a small amino acid (such as Gly or Ala) at this position is important not only for maintaining the functions of the active-site P-loop but, more surprisingly, also important for maintaining the overall structural integrity of NAT enzymes. Our data thus suggest that in addition to its role in substrate binding and selectivity, the active-site P-loop could play a wider structural role in NAT enzymes.
Laboratoire de Cytophysiologie et Toxicologie Cellulaire (EA 1553), Université Paris Diderot-Paris 7, 75005 Paris, France.
Noureddine
N
Atmane
Julien
J
Dairou
Delphine
D
Flatters
Marta
M
Martins
Benjamin
B
Pluvinage
Philippe
P
Derreumaux
Jean-Marie
JM
Dupret
Fernando
F
Rodrigues-Lima
D000105:Acetyl Coenzyme A / Q000737:chemistry; D000409:Alanine / Q000737:chemistry* / Q000235:genetics; D020561:Alphaproteobacteria / Q000201:enzymology*; D020816:Amino Acid Motifs; D001191:Arylamine N-Acetyltransferase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D005998:Glycine / Q000737:chemistry* / Q000235:genetics; D007527:Isoenzymes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism
D001426:Bacterial Proteins; D007527:Isoenzymes; D011994:Recombinant Proteins; D000105:Acetyl Coenzyme A; D001191:Arylamine N-Acetyltransferase; C089384:N-acetyltransferase 1; D000409:Alanine; D005998:Glycine