{PDOC51089}
{PS51089; HP}
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* Headpiece (HP) domain profile *
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Headpiece  is  an ~70-residue F-actin-binding domain present at the C terminus
of  many  cytoskeletal proteins [1]. It was first discovered in the epithelial
brush  border  protein villin, a member of the gelsolin family, which consists
of six gelsolin repeats, followed by the C-terminal headpiece domain [2].

The  headpiece  domain  folds  in  a very compact globular structure organized
around  an extended hydrophobic core (see <PDB:1QQV>) [1]. It is composed of a
highly  alpha-helical C-terminal subdomain and an N-terminal subdomain made up
of  bends  and  turns  with  a  short  alpha-helix.  Most of the actin-binding
residues  identified  by biochemical studies are localized on a single face on
the surface of the domain [3].

Some of the proteins known to contain a headpiece domain are listed below:

 - Eukaryotic villin protein, a Ca(2+)-regulated actin-binding protein. Villin
   has been demonstrated to bundle and sever F-actin [4].
 - Drosophila villin-like protein quail.
 - Vertebrate dematin, an actin-bundling protein.
 - Animal actin-binding LIM (AbLIM) or limatin protein. It may act as scaffold
   protein and may play a role in axon guidance.
 - Vertebrate  advillin  protein.  It  may  function  in  the morphogenesis of
   neuronal cells which form ganglia.
 - Supervillin  protein.  It  forms  a  high-affinity  link  between the actin
   cytoskeleton and the membrane.

The profile we developed covers the whole headpiece domain.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: March 2005 / First entry.

[ 1] Vardar D., Buckley D.A., Frank B.S., McKnight C.J.
     "NMR structure of an F-actin-binding 'headpiece' motif from villin."
     J. Mol. Biol. 294:1299-1310(1999).
     PubMed=10600386; DOI=10.1006/jmbi.1999.3321
[ 2] Finidori J., Friederich E., Kwiatkowski D.J., Louvard D.
     "In vivo analysis of functional domains from villin and gelsolin."
     J. Cell Biol. 116:1145-1155(1992).
     PubMed=1310994
[ 3] Vermeulen W., Vanhaesebrouck P., Van Troys M., Verschueren M.,
     Fant F., Goethals M., Ampe C., Martins J.C., Borremans F.A.
     "Solution structures of the C-terminal headpiece subdomains of human
     villin and advillin, evaluation of headpiece F-actin-binding
     requirements."
     Protein Sci. 13:1276-1287(2004).
     PubMed=15096633; DOI=10.1110/ps.03518104
[ 4] Bretscher A., Weber K.
     "Villin is a major protein of the microvillus cytoskeleton which binds
     both G and F actin in a calcium-dependent manner."
     Cell 20:839-847(1980).
     PubMed=6893424

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