{PDOC50892}
{PS50892; V_SNARE}
{BEGIN}
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* v-SNARE coiled-coil homology domain profile *
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The process  of  vesicular  membrane  fusion  in eukaryotic cells depends on a
conserved fusion  machinery  called  SNARE (soluble N-ethylmaleimide-sensitive
factor (NSF)  attachment  protein (SNAP) receptors). In the process of vesicle
docking, proteins  present  on  the  vesicle  (v-SNARE)  have to bind to their
counterpart  on the target membrane (t-SNARE)  to form a core complex that can
then recruit  the soluble proteins NSF and SNAP. This so called fusion complex
can then  disassemble  after  ATP  hydrolysis  mediated by the ATPase NSF in a
process that leads to membrane fusion and the release of the vesicle contents.
v-SNAREs include proteins homologous to synaptobrevin [1,2,3].

Structurally the  SNARE  complex is generally a four-helix bundle comprised of
three coiled-coil-forming domains from t-SNAREs (see <PDOC50192>) and one from
v-SNARE (see  <PDB:1GL2>).  Although sequence similarity in the t- and v-SNARE
coiled-coil homology  domains  are low there is a striking conservation of the
so-called heptad repeat that is of central importance in forming a coiled-coil
structure. In  a  coiled-coil  motif,  seven  residues  constitute a canonical
heptad and  are designated 'a' through 'g', with 'a' and 'd' being occupied by
hydrophobic residues.  The  association of the four alpha-helices in the SNARE
fusion complex structure produces highly conserved layers of interacting amino
acid side  chains  in  the  center of the four-helix bundle. The center of the
bundle is  made  up of 15 hydrophobic layers from the 'a' and 'd' positions of
the heptad    repeats  of the coiled-coil-forming domains, whereas the central
'ionic' layer  is highly conserved and polar in nature, containing a glutamine
residue in  the  three  t-SNAREs  and  an  arginine  in the v-SNARE, hence the
classification of   v-  and  t-SNAREs as R- and Q-SNAREs, respectively. The v-
SNARE coiled-coil homology domain is around 60 amino acids in length [1,2,3].

The profile  we  developed  cover  the  entire  v-SNARE  coiled-coil  homology
domain.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: December 2002 / New entry.

[ 1] Terrian D.M., White M.K.
     "Phylogenetic analysis of membrane trafficking proteins: a family
     reunion and secondary structure predictions."
     Eur. J. Cell Biol. 73:198-204(1997).
     PubMed=9243180
[ 2] Fasshauer D., Sutton R.B., Brunger A.T., Jahn R.
     "Conserved structural features of the synaptic fusion complex: SNARE
     proteins reclassified as Q- and R-SNAREs."
     Proc. Natl. Acad. Sci. U.S.A. 95:15781-15786(1998).
     PubMed=9861047
[ 3] Scales S.J., Hesser B.A., Masuda E.S., Scheller R.H.
     "Amisyn, a novel syntaxin-binding protein that may regulate SNARE
     complex assembly."
     J. Biol. Chem. 277:28271-28279(2002).
     PubMed=12145319; DOI=10.1074/jbc.M204929200

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