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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 .
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 .
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 β-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 β-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
May 2013 / Text revised; profile added.
PROSITE methods (with tools and information) covered by this documentation:
Hunt L.T., Barker W.C., Chen H.R.
A domain structure common to hemopexin, vitronectin, interstitial collagenase, and a collagenase homolog.
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