Structure and site-directed mutagenesis of a flavoprotein from Escherichia coli that reduces nitrocompounds: alteration of pyridine nucleotide binding by a single amino acid substitution.Kobori, T., Sasaki, H., Lee, W.C., Zenno, S., Saigo, K., Murphy, M.E., Tanokura, M.
(2001) J.Biol.Chem. 276: 2816-2823
- PubMed: 11034992
- DOI: 10.1074/jbc.M002617200
- PubMed Abstract:
The crystal structure of a major oxygen-insensitive nitroreductase (NfsA) from Escherichia coli has been solved by the molecular replacement method at 1.7-A resolution. This enzyme is a homodimeric flavoprotein with one FMN cofactor per monomer and c ...
The crystal structure of a major oxygen-insensitive nitroreductase (NfsA) from Escherichia coli has been solved by the molecular replacement method at 1.7-A resolution. This enzyme is a homodimeric flavoprotein with one FMN cofactor per monomer and catalyzes reduction of nitrocompounds using NADPH. The structure exhibits an alpha + beta-fold, and is comprised of a central domain and an excursion domain. The overall structure of NfsA is similar to the NADPH-dependent flavin reductase of Vibrio harveyi, despite definite difference in the spatial arrangement of residues around the putative substrate-binding site. On the basis of the crystal structure of NfsA and its alignment with the V. harveyi flavin reductase and the NADPH-dependent nitro/flavin reductase of Bacillus subtilis, residues Arg(203) and Arg(208) of the loop region between helices I and J in the vicinity of the catalytic center FMN is predicted as a determinant for NADPH binding. The R203A mutant results in a 33-fold increase in the K(m) value for NADPH indicating that the side chain of Arg(203) plays a key role in binding NADPH possibly to interact with the 2'-phosphate group.
Departments of Applied Biological Chemistry and Biotechnology, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.