{PDOC00732}
{PS00951; ER_LUMEN_RECEPTOR_1}
{PS00952; ER_LUMEN_RECEPTOR_2}
{BEGIN}
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* ER lumen protein retaining receptor signatures *
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Proteins that reside in the lumen of the endoplasmic  reticulum (ER) contain a
C-terminal tetrapeptide (generally K-D-E-L or H-D-E-L) that serves as a signal
for their retrieval (retrograde transport) from subsequent compartments of the
secretory pathway.  The  signal  is  recognized by a receptor molecule that is
believed to cycle between the cis side  of the Golgi apparatus and the ER [1].
This protein  is known  as the  ER lumen protein retaining receptor or also as
the 'KDEL  receptor'.  It  has  been  characterized  in  a variety of species,
including  fungi (gene  ERD2), plants, Plasmodium,  Drosophila and mammals. In
mammals two highly related forms of the receptor are known.

Structurally, the   receptor is a protein of about 220 residues that seems  to
contain seven transmembrane regions [2].  The  N-terminal part (3 residues) is
oriented toward the  lumen  while  the C-terminal  tail (about 12 residues) is
cytoplasmic. There are three lumenal and three cytoplasmic loops.

We developed  two  signature  patterns  for these receptors. The first pattern
corresponds to  the  C-terminal  half of the first cytoplasmic loop as well as
most of  the  second  transmembrane  domain. The second pattern is a perfectly
conserved decapeptide  that  corresponds  to  the  central  part  of the fifth
transmembrane domain.

-Consensus pattern: G-[LIV]-S-x-[KR]-x-[QH]-x-L-[FY]-x-[LIV](2)-[FYW]-x(2)-R-
                    Y
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.

-Consensus pattern: L-E-[SA]-V-A-I-[LM]-P-Q-[LI]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.

-Last update: December 2001 / Patterns and text revised.

[ 1] Pelham H.R.B.
     "Recycling of proteins between the endoplasmic reticulum and Golgi
     complex."
     Curr. Opin. Cell Biol. 3:585-591(1991).
     PubMed=1663369
[ 2] Townsley F.M., Wilson D.W., Pelham H.R.B.
     "Mutational analysis of the human KDEL receptor: distinct structural
     requirements for Golgi retention, ligand binding and retrograde
     transport."
     EMBO J. 12:2821-2829(1993).
     PubMed=8392934

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