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J. Bacteriol., 07 1996, 3803-3808, Vol 178, No. 13
M LaCelle, M Kumano, K Kurita, K Yamane, P Zuber and MM Nakano
A gene, hmp, which encodes a ubiquitous protein homologous to hemoglobin
was isolated among genes from Bacillus subtilis that are induced under
anaerobic conditions. The hmp protein belongs to the family of two-domain
flavohemoproteins, homologs of which have been isolated from various
organisms such as Escherichia coli, Alcaligenes eutrophus, and
Saccharomyces cerevisiae. These proteins consist of an amino-terminal
hemoglobin domain and a carboxy-terminal redox active site domain with
potential binding sites for NAD(P)H and flavin adenine dinucleotide. The
expression of hmp is strongly induced upon oxygen limitation, and the
induction is dependent on a two-component regulatory pair, ResD and ResE,
an anaerobic regulator, FNR, and respiratory nitrate reductase, NarGHJI.
The requirement of FNR and NarGHJI for hmp expression is completely
bypassed by the addition of nitrite in the culture medium, indicating that
fnr is required for transcriptional activation of narGHJI, which produces
nitrite, leading to induction of hmp expression. In contrast, induction of
hmp was still dependent on resDE in the presence of nitrite. A defect in
hmp in B. subtilis has no significant effect on anaerobic growth.
Copyright © 1996, American Society for Microbiology
Oxygen-controlled regulation of the flavohemoglobin gene in Bacillus subtilis
Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, Shreveport, Louisiana 71130-3932, USA.
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