title: Binding of the anti-tubercular drug isoniazid to the arylamine N-acetyltransferase protein from Mycobacterium smegmatis.
abstract: Isoniazid is a frontline drug used in the treatment of tuberculosis (TB). Isoniazid is a prodrug, requiring activation in the mycobacterial cell by the catalase/peroxidase activity of the katG gene product. TB kills two million people every year and the situation is getting worse due to the increase in prevalence of HIV/AIDS and emergence of multidrug-resistant strains of TB. Arylamine N-acetyltransferase (NAT) is a drug-metabolizing enzyme (E.C. 2.1.3.5). NAT can acetylate isoniazid, transferring an acetyl group from acetyl coenzyme A onto the terminal nitrogen of the drug, which in its N-acetylated form is therapeutically inactive. The bacterium responsible for TB, Mycobacterium tuberculosis, contains and expresses the gene encoding the NAT protein. Isoniazid binds to the NAT protein from Salmonella typhimurium and we report here the mode of binding of isoniazid in the NAT enzyme from Mycobacterium smegmatis, closely related to the M. tuberculosis and S. typhimurium NAT enzymes. The mode of binding of isoniazid to M. smegmatis NAT has been determined using data collected from two distinct crystal forms. We can say with confidence that the observed mode of binding of isoniazid is not an artifact of the crystallization conditions used. The NAT enzyme is active in mycobacterial cells and we propose that isoniazid binds to the NAT enzyme in these cells. NAT activity in M. tuberculosis is likely therefore to modulate the degree of activation of isoniazid by other enzymes within the mycobacterial cell. The structure of NAT with isoniazid bound will facilitate rational drug design for anti-tubercular therapy.
authors.affiliation: Department of Pharmacology, Oxford University, Mansfield Road, Oxford, OX1 3QT, United Kingdom. james.sandy@pharm.ox.ac.uk
authors.forename: James
authors.initials: J
authors.lastname: Sandy
authors.forename: Simon
authors.initials: S
authors.lastname: Holton
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Fullam
authors.forename: Edith
authors.initials: E
authors.lastname: Sim
authors.forename: Martin
authors.initials: M
authors.lastname: Noble
mesh_terms: D000995:Antitubercular Agents / Q000378:metabolism*; D001191:Arylamine N-Acetyltransferase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D020134:Catalytic Domain; D003460:Crystallization; D007538:Isoniazid / Q000378:metabolism*; D007700:Kinetics; D020102:Mycobacterium smegmatis / Q000201:enzymology* / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
chemical_list: D000995:Antitubercular Agents; D002374:Catalase; D009195:Peroxidase; D001191:Arylamine N-Acetyltransferase; D007538:Isoniazid
references.citation: Microbiology. 2001 Dec;147(Pt 12):3295-302
references.pmid: 11739761
references.citation: Annu Rev Biochem. 1995;64:29-63
references.pmid: 7574484
references.citation: J Biol Chem. 1971 May 25;246(10):3250-8
references.pmid: 5103348
references.citation: J Biol Chem. 2004 Sep 10;279(37):38991-9
references.pmid: 15231843
references.citation: J Am Chem Soc. 2001 Apr 25;123(16):3832-3
references.pmid: 11457121
references.citation: Nature. 1992 Aug 13;358(6387):591-3
references.pmid: 1501713
references.citation: J Exp Med. 2004 May 3;199(9):1191-9
references.pmid: 15117974
references.citation: Biochem J. 2005 Aug 15;390(Pt 1):115-23
references.pmid: 15869465
references.citation: J Mol Biol. 2002 May 10;318(4):1071-83
references.pmid: 12054803
references.citation: Prog Lipid Res. 1998 Jul-Aug;37(2-3):143-79
references.pmid: 9829124
references.citation: Acta Crystallogr A. 1991 Mar 1;47 ( Pt 2):110-9
references.pmid: 2025413
references.citation: J Biol Chem. 2004 May 21;279(21):22131-7
references.pmid: 15039438
references.citation: Mol Microbiol. 2000 Nov;38(3):514-25
references.pmid: 11069675
references.citation: Mol Microbiol. 2001 Oct;42(2):309-17
references.pmid: 11703656
references.citation: Bioorg Med Chem Lett. 2003 Aug 4;13(15):2527-30
references.pmid: 12852958
references.citation: J Bacteriol. 1993 Jul;175(13):4255-9
references.pmid: 8320241
references.citation: Bioorg Med Chem. 2003 Apr 3;11(7):1227-34
references.pmid: 12628650
references.citation: Microbes Infect. 2000 May;2(6):659-69
references.pmid: 10884617
references.citation: J Bacteriol. 1999 Feb;181(4):1343-7
references.pmid: 9973365
references.citation: Protein Expr Purif. 2003 Jan;27(1):75-84
references.pmid: 12509987
references.citation: Acta Crystallogr D Biol Crystallogr. 1994 Sep 1;50(Pt 5):760-3
references.pmid: 15299374
references.citation: J Biol Chem. 2002 Apr 5;277(14):12175-81
references.pmid: 11799105
references.citation: Protein Expr Purif. 2002 Feb;24(1):138-51
references.pmid: 11812235
references.citation: Science. 1998 Jan 2;279(5347):98-102
references.pmid: 9417034
references.citation: Protein Eng. 1995 Feb;8(2):127-34
references.pmid: 7630882
references.citation: Biochim Biophys Acta. 2003 Mar 17;1620(1-3):8-14
references.pmid: 12595067