Article

cis- and trans-acting elements involved in regulation of norB (norZ), the gene encoding nitric oxide reductase in Neisseria gonorrhoeae.

Department of Microbiology and Immunology, School of Medicine and Dentistry, University of Rochester, Box 672, 601 Elmwood Avenue, Rochester, NY 14642, USA.
Microbiology (impact factor: 3.06). 02/2008; 154(Pt 1):226-39. DOI:10.1099/mic.0.2007/010470-0 pp.226-39
Source: PubMed

ABSTRACT The ability of Neisseria gonorrhoeae to reduce nitric oxide (NO) may have important immunomodulatory effects on the host during infection. Therefore, a comprehensive understanding of the regulatory mechanism of the nitric oxide reductase gene (norB) needs to be elucidated. To accomplish this, we analysed the functional regions of the norB upstream region. The promoter contains an extended -10 motif (TGNTACAAT) that is required for high-level expression. Deletion and substitution analysis of the norB upstream region revealed that no sequence upstream of the -10 motif is involved in norB regulation under anaerobic conditions or in the presence of NO. However, replacement of a 29 bp inverted repeat sequence immediately downstream of the extended -10 motif gave high levels of aerobic expression of a norB : : lacZ fusion. Insertional inactivation of gonococcal nsrR, predicted to bind to this inverted repeat sequence, resulted in the loss of norB repression and eliminated NO induction capacity. Single-copy complementation of nsrR in trans restored regulation of both norB transcription and NorB activity by NO. In Escherichia coli, expression of a gonococcal nsrR gene repressed gonococcal norB; induction of norB occurred in the presence of exogenously added NO. NsrR also regulates aniA and dnrN, as well as its own expression. We also determined that Fur regulates norB by a novel indirect activation method, by preventing the binding of a gonococcal ArsR homologue, a second repressor whose putative binding site overlaps the Fur binding site.

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Keywords

29 bp inverted repeat sequence
 
Escherichia coli
 
extended -10 motif
 
functional regions
 
Fur binding site
 
Fur regulates norB
 
gonococcal ArsR homologue
 
gonococcal nsrR gene repressed gonococcal norB
 
induction capacity
 
inverted repeat sequence
 
lacZ fusion
 
nitric oxide reductase gene
 
norB
 
NorB activity
 
norB regulation
 
norB repression
 
norB transcription
 
norB upstream region
 
novel indirect activation method
 
second repressor
 

Vincent Isabella