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Insight into the structure of Mesorhizobium loti arylamine N ‐acetyltransferase 2 (MLNAT2): A biochemical and computational study
Author(s) -
Dairou Julien,
Flatters Delphine,
Chaffotte Alain F.,
Pluvinage Benjamin,
Sim Edith,
Dupret Jean-Marie,
Rodrigues-Lima Fernando
Publication year - 2006
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2006.02.033
Subject(s) - nat , arylamine n acetyltransferase , gene isoform , stereochemistry , prokaryote , mesorhizobium , biology , biochemistry , enzyme , peptide sequence , homology modeling , chemistry , acetylation , genetics , gene , physics , bacteria , rhizobia , symbiosis , quantum mechanics
The arylamine N ‐acetyltransferases (NAT; EC 2.3.1.5) are xenobiotic‐metabolizing enzymes (XME) that catalyze the transfer of an acetyl group from acetylCoA (Ac‐CoA) to arylamine, hydrazines and their N ‐hydroxylated metabolites. Eukaryotes may have up to three NAT isoforms, but Mesorhizobium loti is the only prokaryote with two functional NAT isoforms (MLNAT1 and MLNAT2). The three‐dimensional structure of MLNAT1 has been determined (Holton, S.J., Dairou, J., Sandy, J., Rodrigues‐Lima, F., Dupret, J.M., Noble, M.E.M. and Sim, E. (2005) Structure of Mesorhizobium loti arylamine N ‐acetyltransferase 1. Acta Cryst, F61, 14–16). No MLNAT2 crystals have yet been produced, despite the production of sufficient quantities of pure protein. Using purified recombinant MLNAT1 and MLNAT2, we showed here that MLNAT1 was intrinsically more stable than MLNAT2. To test whether different structural features could explain these differences in intrinsic stability, we constructed a high‐quality homology model for MLNAT2 based on far UV‐CD data. Despite low levels of sequence identity with other prokaryotic NAT enzymes (≈28% identity), this model suggests that MLNAT2 adopts the characteristic three‐domain NAT fold. More importantly, molecular dynamics simulations on the structures of MLNAT1 and MLNAT2 suggested that MLNAT2 was less stable than MLNAT1 due to differences in amino‐acid sequence/structure features in the α/β lid domain.