{PDOC00023}
{PS00024; HEMOPEXIN_1}
{PS51642; HEMOPEXIN_2}
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* Hemopexin domain signature and hemopexin repeat profile *
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Hemopexin is a  serum glycoprotein that  binds  heme and transports it  to the
liver for breakdown and iron recovery, after  which the free hemopexin returns
to the circulation.  Structurally hemopexin consists of  two similar halves of
approximately two hundred  amino acid residues  connected  by a histidine-rich
hinge region. Each half is itself formed by the repetition of  a basic unit of
some 35 to 45 residues.  Hemopexin-like domains have  been found [1,2]  in two
other types of proteins:

 - In  vitronectin  (also  known  as  complement S protein and serum spreading
   factor), a multifunctional adhesion glycoprotein that is present abundantly
   in plasma  and  the  extracellular  matrix.  Vitronectin  consists of an N-
   terminal somatomedin   B   (see   <PDOC00453>)  and,  like  hemopexin,  two
   hemopexin-like domains [3].
 - In  most  members  of the matrix metalloproteinases family (matrixins) (see
   <PDOC00129>): MMP-1,  MMP-2,  MMP-3,  MMP-8, MMP-9, MMP-10, MMP-11, MMP-12,
   MMP-13, MMP-14,  MMP-15,  MMP-16,  MMP-17,  MMP-18, MMP-19, MMP-20, MMP-24,
   and MMP-25. These zinc endoproteases have a single hemopexin-like domain in
   their C-terminal section [4].

It is suggested that the  hemopexin domain facilitates binding to a variety of
molecules and proteins.

The hemopexin  domain  exhibits  the  shape of an oblate ellipsoidal disk. The
polypeptide chain  is organized in four beta-sheet (blades) I to IV, which are
almost symmetrically  arranged  around  a  central  axis in consecutive order,
giving rise to the formation of a four-bladed propeller (see <PDB:1PEX>). Each
propeller blade  or  repeat  is  made  up  of  four  antiparallel beta-strands
connected in a W-like strand topology, and is strongly twisted [5,6].

We developed  both  a  pattern  and  a  profile. The signature pattern for the
hemopexin domain  has  been  derived  from  the best conserved region which is
located at  the  beginning of the second repeat. The profile covers the entire
hemopexin repeat.

-Consensus pattern: [LIFAT]-{IL}-x(2)-W-x(2,3)-[PE]-x-{VF}-[LIVMFY]-[DENQS]-
                    [STA]-[AV]-[LIVMFY]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in Swiss-Prot: 11.

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

-Last update: May 2013 / Text revised; profile added.

[ 1] Hunt L.T., Barker W.C., Chen H.R.
     "A domain structure common to hemopexin, vitronectin, interstitial
     collagenase, and a collagenase homolog."
     Protein Seq. Data Anal. 1:21-26(1987).
     PubMed=2451821
[ 2] Stanley K.K.
     "Homology with hemopexin suggests a possible scavenging function for
     S-protein/vitronectin."
     FEBS Lett. 199:249-253(1986).
     PubMed=2422056
[ 3] Marioli D.J., Zarkadis I.K.
     "The vitronectin gene in rainbow trout: cloning, expression and
     phylogenetic analysis."
     Fish Shellfish Immunol. 24:18-25(2008).
     PubMed=17981477; DOI=10.1016/j.fsi.2007.07.007
[ 4] Piccard H., Van den Steen P.E., Opdenakker G.
     "Hemopexin domains as multifunctional liganding modules in matrix
     metalloproteinases and other proteins."
     J. Leukoc. Biol. 81:870-892(2007).
     PubMed=17185359; DOI=10.1189/jlb.1006629
[ 5] Gomis-Rueth F.X., Gohlke U., Betz M., Knaeuper V., Murphy G.,
     Lopez-Otin C., Bode W.
     "The helping hand of collagenase-3 (MMP-13): 2.7 A crystal structure
     of its C-terminal haemopexin-like domain."
     J. Mol. Biol. 264:556-566(1996).
     PubMed=8969305; DOI=10.1006/jmbi.1996.0661
[ 6] Gaur V., Qureshi I.A., Singh A., Chanana V., Salunke D.M.
     "Crystal structure and functional insights of hemopexin fold protein
     from grass pea."
     Plant Physiol. 152:1842-1850(2010).
     PubMed=20147493; DOI=10.1104/pp.109.150680

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