{PDOC51753}
{PS51753; HBM}
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* HBM domain profile *
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The helical  bimodular  (HBM)  domain  is  a  small molecule binding domain of
around 250 amino acids. It is found in Bacteria and Archaea but is absent from
eukaryotes and  forms  part  of chemoreceptors (see <PDOC00465>) and histidine
kinases (see  <PDOC50109>).  The  HBM  domain  is  composed  of two structural
modules, each of which recognizes a different type of ligand. The conservation
of amino  acids  in the ligand binding sites of both modules suggests that HBM
family members recognize similar ligands [1].

The HBM  domain  is  composed of six helices linked by loops (see <PDB:2YFB>).
Two short  helices  (alpha1  and  alpha2) at the membrane-proximal part of the
structure are  followed  by the long helix alpha3. This segment is followed by
another couple  of  short  helices (alpha4 and alpha5) and a second long helix
alpha6, which is predicted to continue as a transmembrane helix. The structure
can be  understood  as a duplication of a structural element made of two short
and a  long helix. The six helices of the HBM domain arrange into two modules,
each forming  a four-helix bundle. The membrane proximal module is composed of
alpha1, alpha2, the N-terminal segment of alpha 3, and  the C-terminal segment
of alpha6. The membrane distal module is composed of the C-terminal segment of
alpha3, helices alpha4 and alpha5, and the the N-terminal part of alpha6 [2].

The profile we developed covers the entire HBM domain.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: April 2015 / First entry.

[ 1] Ortega A., Krell T.
     "The HBM domain: introducing bimodularity to bacterial sensing."
     Protein Sci. 23:332-336(2014).
     PubMed=24347303; DOI=10.1002/pro.2410
[ 2] Pineda-Molina E., Reyes-Darias J.-A., Lacal J., Ramos J.L.,
     Garcia-Ruiz J.M., Gavira J.A., Krell T.
     "Evidence for chemoreceptors with bimodular ligand-binding regions
     harboring two signal-binding sites."
     Proc. Natl. Acad. Sci. U.S.A. 109:18926-18931(2012).
     PubMed=23112148; DOI=10.1073/pnas.1201400109

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