1YLU

The structure of E. coli nitroreductase with bound acetate, crystal form 2

Summary for 1YLU

• Entry DOI: 10.2210/pdb1ylu/pdb
• Related: 1ICR 1ICU 1ICV 1YKI 1YLR
• Descriptor: Oxygen-insensitive NAD(P)H nitroreductase, ACETATE ION, FLAVIN MONONUCLEOTIDE, ... (4 entities in total)
• Functional Keywords: oxidoreductase, oxygen-insensitive nad(p)h nitroreductase
• Biological source: Escherichia coli
• Total number of polymer chains: 2
• Total formula weight: 48964.18

Authors

Race, P.R.,Lovering, A.L.,Green, R.M.,Ossor, A.,White, S.A.,Searle, P.F.,Wrighton, C.J.,Hyde, E.I. (deposition date: 2005-01-19, release date: 2005-02-08, Last modification date: 2023-08-23)

Primary citation

Race, P.R.,Lovering, A.L.,Green, R.M.,Ossor, A.,White, S.A.,Searle, P.F.,Wrighton, C.J.,Hyde, E.I.
Structural and mechanistic studies of Escherichia coli nitroreductase with the antibiotic nitrofurazone. Reversed binding orientations in different redox states of the enzyme.
J.Biol.Chem., 280:13256-13264, 2005

PubMed Abstract: The antibiotics nitrofurazone and nitrofurantoin are used in the treatment of genitourinary infections and as topical antibacterial agents. Their action is dependent upon activation by bacterial nitroreductase flavoproteins, including the Escherichia coli nitroreductase (NTR). Here we show that the products of reduction of these antibiotics by NTR are the hydroxylamine derivatives. We show that the reduction of nitrosoaromatics is enzyme-catalyzed, with a specificity constant approximately 10,000-fold greater than that of the starting nitro compounds. This suggests that the reduction of nitro groups proceeds through two successive, enzyme-mediated reactions and explains why the nitroso intermediates are not observed. The global reaction rate for nitrofurazone determined in this study is over 10-fold higher than that previously reported, suggesting that the enzyme is much more active toward nitroaromatics than previously estimated. Surprisingly, in the crystal structure of the oxidized NTR-nitrofurazone complex, nitrofurazone is oriented with its amide group, rather than the nitro group to be reduced, positioned over the reactive N5 of the FMN cofactor. Free acetate, which acts as a competitive inhibitor with respect to NADH, binds in a similar orientation. We infer that the orientation of bound nitrofurazone depends upon the redox state of the enzyme. We propose that the charge distribution on the FMN rings, which alters upon reduction, is an important determinant of substrate binding and reactivity in flavoproteins with broad substrate specificity.

PubMed: 15684426
DOI: 10.1074/jbc.M409652200

Experimental method

X-RAY DIFFRACTION (2 Å)