|CD11b||ITGAM (integrin αM), α-chain of C3biR, CR3, Mac-1, Mo1|
|Molecule Type||Antigen Expression||Molecular Weight|
Min / Max
|Non-lineage Restricted Molecule|
Type 1 glycoprotein
|165 / 165|
170 / 170
|CD11b is expressed on granulocytes, monocytes, NK cells, and subsets of T and B cells.|
|MOLECULAR FAMILY NAME: Belongs to the integrin a chain family.|
CD11b is a single-pass type-1 α chain 1136 aa glycoprotein. It contains an 1092 aa extracellular domain which contains 7 tandem repeats domains that have been modeled to resemble a b propeller fold, an I-domain and 19 potential N-glycosylation sites, a 26 aa transmembrane domain and a 19 aa cytoplasmic domain. A major ligand binding site has been mapped to a von Willebrand A domain, I domain, which is inserted between repeats 2 and 3. The structure of the CD11b I domain is shown to resemble a classic a-b dinucleotide binding fold. It is expressed as a non-covalently linked heterodimer with CD18.
An extra codon CAG between bp 1580 and 1581 is found in some CD11b cDNAs. Genomic sequencing revealed that this codon forms the last 3 bases of the intronic acceptor located between exons 13 and 14 of CD11b, suggesting an alternative splicing. Receptors with or without the extra codon are functionally indistinguishable.
There are 19 potential N-glycosylation sites.
|Ligands of CD11b/CD18 (Mac-1, CR3) are 1C3b, CD54 (ICAM-1), fibrinogen, Kininogen, haptoglobin, Factor X, CD23, CD102, (ICAM-2), heparin, β-glucan, LPS complexed with LPS binding protein (LPS/LPB), neutrophil inhibitory factor of Ancylostoma caninum, filamentous hemagglutinin from Bordetella pertussis, gp63 of Leishmenia donovani and WI-1 antigen of Blastomyces dermatitidis.|
LIGANDS AND MOLECULES ASSOCIATED WITH CD11b
The binding site for some ligands such as iC3b, CD54 (ICAM-1), CD102 (ICAM-2), and fibrinogen is in the A I-domain. The structural basis for many of the reported CD11b/CD18 ligands is presently unclear. There is increasing evidence that CD11b/CD18 is associated with many other membrane proteins at the cell surface including CD14, CD87, and the Fcg receptors CD16 and CD32.
|CD11b/CD18 Mac-1 is also known as the complement receptor type 3 (CR3) because of its binding to the iC3b complement fragment on opsonized targets. It also mediates the subsequent ingestion process. CD11b/CD18 is also important in the transendothelial migration of monocytes and neutrophils whose interactions occur with stimulated endothelium. There is adherence of the polymorphonuclear neutrophils and monocytes to fibrinogen and the CD54 endothelium. Its association with other membrane proteins may account for the many signaling functions of CD11b/CD18. Most binding activities involve the I-domain of CD11b. Neutrophil respiratory burst or degranulation is stimulated by other receptors such as FcR or C5a and channeled through CD11b/CD18: spreading, chemotaxis and apoptosis. CD11b is important in the phagocytosis of iC3b or IgG complement coated particles. |
BIOCHEMICAL ACTIVITY: No information.
DISEASE RELEVANCE AND FUNCTION OF CD11b IN INTACT ANIMAL
CD11b is absent in leukocyte adhesion deficiency (LAD-1) patients who have major problems with bacterial infections and is the target of anti-inflammatory drug therapeutics.
|MOLECULAR INTERACTIONS -|
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD11b
SUBSTRATES: No information.
ENZYMES WHICH MODIFY CD11b: No information.
Database accession numbers
Revised June 25, 2008