The extracellular sushi domain is characterized by a consensus sequence
spanning ~60 residues containing four invariant cysteine residues forming two
disulfide-bridges (I-III and II-IV), a highly conserved tryptophan, and
conserved glycine, proline, and hydrophobic residues . Sushi domains are
known to be involved in many recognition processes, including the binding of
several complement factors to fragments C3b and C4b . The sushi domain is
also known as the complement controle protein (CCP) module or the short
consensus repeat (SCR).
Several structure of the sushi domain have been solved (see for example
<PDB:1HCC>) . The sushi domain folds into a small and compact hydrophobic
core enveloped by six β-strands and stabilized by two disulfide bridges.
The relative structural orientation of the β-2 and β-4 strands is shared
by all the sushi structures, whereas the topology of the other strands
relative to this central conserved core is variable, especially at the regions
that form the interfaces with the preceding and following domains .
Some proteins known to contain a sushi domain:
Mammalian complement receptor type 1 and 2. They mediate cellular binding
of particles and immune complexes that have activated complement.
Mammalian C4b-binding protein α chain. It binds as a cofactor to
C3b/C4b inactivator, which then hydrolyzes the complement fragment C4b.
Mammalian complement factor H-related protein 2. It might be involved in
Mammalian membrane cofactor protein (MCP), an important membrane protein
for protecting host cells from damage by complement. MCP possesses cofactor
activity for inactivation of C3b and C4b by serum factor I.
Mammalian complement decay-accelerating factor (DAF). This protein
recognizes C4b and C3b fragments that condense with cell-surface hydroxyl
or amino groups when nascent C4b and C3b are locally generated during C4
and C3 activation. Interaction of DAF with cell-associated C4b and C3b
polypeptides interferes with their ability to catalyze the conversion of C2
and factor B to enzymatically active C2a and Bb and thereby prevents the
formation of C4b2a and C3bBb, the amplification convertases of the
Mammalian β-2-glycoprotein I or apolipoprotein H. It binds to various
kinds of negatively charged substances such as heparin, phospholipids, and
dextran sulfate. It may prevent activation of the intrinsic blood
coagulation cascade by binding to phospholipids on the surface of damaged
Mammalian P-selectin, a Ca(2+)-dependent receptor for myeloid cells that
binds to carbohydrates on neutrophils and monocytes. It mediates the
interaction of activated endothelial cells or platelets with leukocytes.
Mammalian neurocan core protein. It may modulate neuronal adhesion and
neurite growth during development by binding to neural cell adhesion
molecules (NG-CAM and N-CAM).
Mammalian complement C2. It is part of the classical pathway of the
complement system. It is cleaved by activated factor C1 into two fragments:
C2b and C2a. C2a, a serine protease, then combines with complement factor
4b to generate the C3 or C5 convertase.
Mammalian mannan-binding lectin serine protease 2. A trypsin protease that
presumably plays an important role in the initiation of the mannose-binding
lectin (MBL) complement activation pathway. After activation it cleaves C4
generating C4a and C4b.
Mammalian thyroid peroxidase, a key enzyme in the process of thyroid
Mammalian γ-aminobutyric acid type B receptor, subunit 1 (GABA-B
Mammalian haptoglobin. It combines with free plasma hemoglobin, preventing
loss of iron through the kidneys and protecting the kidneys from damage by
hemoglobin, while making the hemoglobin accessible to degradative enzymes.
Drosophila locomotion-related protein Hikaru genki.
Viral complement control protein. It serves to protect the virus against
complement attack by inhibiting both classical and alternative pathways of
complement activation. It binds C3b and C4b.
The profile we developed covers the whole sushi domain.
December 2003 / First entry.
PROSITE method (with tools and information) covered by this documentation:
Reid K.B., Day A.J.
Structure-function relationships of the complement components.
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