{PDOC51118}
{PS51118; HTH_HXLR}
{BEGIN}
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* HxlR-type HTH domain profile *
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The  hxlR-type  HTH  domain  is  a  domain  of  ~90-100 amino acids present in
putative  transcription  regulators  with  a  winged  helix-turn-helix  (wHTH)
structure.  The  domain is named after Bacillus subtilis hxlR, a transcription
activator  of  the hxlAB operon involved in the detoxification of formaldehyde
[1].  The hxlR-type domain forms the core of putative transcription regulators
and  of  hypothetical  proteins occurring in eubacteria as well as in archaea.
The  sequence  and  structure of hxlR-type proteins show similarities with the
marR-type wHTH (see <PDOC00861>) [2].

The  crystal  structure  of  ytfH  resembles the DNA-binding domains of winged
helix  proteins  (see  <PDB:1YYV>),  containing a three helix (H) bundle and a
three-stranded     antiparallel    beta-sheet    (B)    in    the    topology:
H1-H2-B1-H3-H4-B2-B3-H5-H6.   This  topology  corresponds  with  that  of  the
marR-type   DNA-binding   domain,   wherein  helices  3  and  4  comprise  the
helix-turn-helix motif and the beta-sheet is called the wing.

Some proteins known to contain a hxlR-type HTH domain:

 - Bacillus  subtilis  hxlR,  a  transcription  activator  for  enzymes of the
   ribulose monophosphate pathway, which can be induced by formaldehyde.
 - Escherichia  coli and Salmonella typhimurium ytfH, a hypothetical protein.
 - Fusobacterium  mortiferum  malR,  a potential regulator of the malBH operon
   involved in the metabolism of sucrose isomers [3].

The profile we developed covers the entire hxlR-type HTH domain.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.

-Last update: April 2005 / First entry.

[ 1] Yasueda H., Kawahara Y., Sugimoto S.
     "Bacillus subtilis yckG and yckF encode two key enzymes of the
     ribulose monophosphate pathway used by methylotrophs, and yckH is
     required for their expression."
     J. Bacteriol. 181:7154-7160(1999).
     PubMed=10572115
[ 2] Huffman J.L., Brennan R.G.
     "Prokaryotic transcription regulators: more than just the
     helix-turn-helix motif."
     Curr. Opin. Struct. Biol. 12:98-106(2002).
     PubMed=11839496
[ 3] Pikis A., Immel S., Robrish S.A., Thompson J.
     "Metabolism of sucrose and its five isomers by Fusobacterium
     mortiferum."
     Microbiology 148:843-852(2002).
     PubMed=11882720

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