SR-I,II Scavenger R-AI, Scavenger R-AII
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Lineage Restricted Molecule
Type 2 glycoprotein
Macrophage
75 / 225

Expression
The major sites of scavenger receptors 1 and 2 expression are tissue macrophages.  Inflammatory stimuli upregulate the expression.  The scavenger receptor has been identified in atherosclerotic lesions of human tissues.

Structure
SR-I and II are a homotrimeric type 2 glycoproteins.  SR-1 is a member of the Group A scavenger receptor cysteine- rich (SRCR) superfamily.  It is not known if naturally occurring receptors are homotrimers or heterotrimers of type 1 and 2 proteins.  The bovine sequence was deteremined 1st and is 70% identical to the human sequence.  The mature type 1 receptor is comprised of 50 aa N-terminal cytoplasmic sequence, a 26 aa transmembrane sequence, a 75 aa sequence with no homology to other proteins, a 121 aa sequence predicted to have an a  helical coiled-coil structure, a 69 aa collagen-like domain, and a C-terminal SRCR domain.  The type 2 receptor is identical to the type 1 receptor to the end of the collagen-like sequence, but the C-terminal scavenger receptor domain is replaced by a 17 aa segment.  The 2 scavenger receptors are generated by alternative mRNA splicing.  The type 1 receptor has an overall structure similar to MARCO, both having a C-terminal SRCR domain.  The scavenger receptor has a shorter collagenous region than MARCO.

MOLECULAR MASS
Cell Type Unreduced Reduced
220 kDa 77 kDa



Ligands
Scavenger receptors 1 and 2 bind modified low density lipoproteins.  Both receptors have a similar broad specificity for polyanionic ligands including cell surface components of gram-positive and gram-negative bacteria.  There is evidence from mutagenesis studies for their ligand binding properties being located in the collagenous region.  Scavenger receptors 1 and 2 bind b-amyloid fibrils.

Function
Roles in the clearance of microbes and damaged or apoptotic cells and in recirculation are postulated.

Comments


Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
MouseA38860P30204M36817
MouseM59445
MouseP30204M36818
MouseM59446
Antibodies

Revised June 25, 2008


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