Mf. Anjum et al., RESPONSE OF THE NAD(P)H-OXIDIZING FLAVOHAEMOGLOBIN (HMP) TO PROLONGEDOXIDATIVE STRESS AND IMPLICATIONS FOR ITS PHYSIOLOGICAL-ROLE IN ESCHERICHIA-COLI, FEMS microbiology letters, 166(2), 1998, pp. 219-223
The Escherichia coli flavohaemoglobin (Hmp) has a globin-like N-termin
al domain and a ferredoxin-NADP-reductase-like C-terminal domain. We s
how here that purified Hmp oxidises both NADH and NADPH with K-m value
s of 1.8 and 19.6 mu M, respectively. Prolonged incubation of a hmp-la
cZ fusion strain with the redox cycling agent paraquat resulted in a 2
8-fold induction of hmp gene expression, nearly 3-fold higher than aft
er short periods of exposure. A strain overproducing Hmp was significa
ntly more sensitive to paraquat than was the wild-type strain but, in
vitro, purified Hmp was not an effective NADPH-paraquat diaphorase. Pr
olonged incubation of a wild-type strain with paraquat increased intra
cellular Hmp to spectrally detectable levels. (C) 1998 Federation of E
uropean Microbiological Societies. Published by Elsevier Science B.V.
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