ML macrophage lectin, M-ASGP-BP (rat), MMGL (mouse)
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Lineage Restricted Molecule
Type 2 glycoprotein
Macrophage
30 / 40

Expression
RNA analysis suggests that in the mouse the molecule is expressed at low levels on resident peritoneal macrophages and is upregulated on thioglycollate-elicited peritoneal macrophages.  Similarly, in the rat the antigen appears to be restricted to macrophages.

Structure
ML names: Macrophage asialoglycoprotein binding protein (M-ASGP) (rat); Macrophage galactose/N-acetylgalactosamine-specific lectin (MMGL) (mouse).

Human macrophage lectin (HML) is a single chain type 2 glycoprotein.  It is comprised of an1 extracellular C-type lectin domain.  It is the homologue of the rat macrophage asialoglycoprotein receptor (M-ASGP-BP), the mouse macrophage galactose/N-acetylgalactosamine-specific lectin (MMGL) and is closely related to other human C-type lectins such as the human hepatic lectin 1 (HHL-1) with a 56% identity and human hepatic lectin 2 (HHL-2) with 45% identity.  The C-type lectin domains of the lectins have the greatest similarity with 69% between HML and HHL-1, and 63% between HML and HHL-2.  The cytoplasmic domains of the lectins are more poorly conserved.  Additionally, the HML and HHL-1/HHL-2 proteins differ through the presence of a 24 aa insertion in the extracellular neck region of HML which is also found in the mouse and rat homologues.

MOLECULAR MASS
Cell Type Unreduced Reduced
34-36 kDa


Ligands
HML is a lectin that binds galactose and N-acetylgalactosamine carbohydrate groups in a calcium-dependent manner. A weaker interaction between HML and fucose is also observed.

Function
The presence of a YENF internalization motif in the cytoplasmic domain suggests that the lectin is likely to be involved in receptor-mediated endocytosis.  Recombinant HML expressed in E. coli has been shown to strongly bind glycopeptides carrying 3 consecutive N-acetylgalactosamine-Ser/Thr residues known as Tn antigen, which is a human carcinoma-associated epitope, implicating a role in recognition by tumoricidal macrophages.

Comments

 

 



Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
MouseP49300S36676
RatP49301J05495
Antibodies

Revised June 25, 2008


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