{PDOC50906}
{PS50906; NIT}
{BEGIN}
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* Nitrate and nitrite sensing (NIT) domain profile *
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The  nitrate  and  nitrite sensing (NIT) domain is an about 250-residue sensor
domain  which  has  been  detected  in  various  receptor components of signal
transduction  pathways  from  different bacterial lineages. All proteins which
contain  a  NIT  domain belong to one of the four known classes of prokaryotic
signal transduction proteins, namely:

 - Intracellular transcription anti-termination regulators,
 - Sensor histidine kinases,
 - Methyl-accepting chemotaxis proteins,
 - Diguanylate cyclases and phosphodiesterases.

NIT-containing  receptors  regulate cellular functions such as gene expression
(transcription   anti-terminators   and   histidine  kinases),  cell  motility
(chemotaxis   receptors)   and   enzyme  activity  (diguanylate  cyclases  and
phosphodiesterases),   in  response  to  changes  in  nitrate  and/or  nitrite
concentrations.  The  NIT  domain  is  found  both  as an extracellular and an
intracellular  sensor.  It  can be found in association with others signalling
domains   like   ANTAR,   HAMP   (see  <PDOC50885>),  MCP,  Hemerythrins  (see
<PDOC00476>),  CHASE  (see  <PDOC50839>),  GGDEF  (see  <PDOC50887>), PAS (see
<PDOC50112>),  EAL  (see  <PDOC50883>), HK (see <PDOC50109>), GAF, REC and HPt
(see <PDOC50894>).

The NIT domain is predicted to be all alpha-helical. Several conserved charged
residues  form  a  signature  for  the  NIT  domain:  the  Glu-Arg  couple  in
alpha-helix  1,  Asp  in  alpha-helix 2, Arg in alpha-helix 3, and the charged
residue  (Glu  or  Arg)  in  alpha-helix  5.  In addition a conserved aromatic
residue is found in alpha-helix 10 [1].

The profile we developed covers the entire core of the NIT domain.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: August 2003 / First entry.

[ 1] Shu C.J., Ulrich L.E., Zhulin I.B.
     "The NIT domain: a predicted nitrate-responsive module in bacterial
     sensory receptors."
     Trends Biochem. Sci. 28:121-124(2003).
     PubMed=12633990

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