Reactome | MBL binds to repetitive carbohydrate structures on the surfaces of viruses, bacteria, fungi, and protozoa

MBL binds to repetitive carbohydrate structures on the surfaces of viruses, bacteria, fungi, and protozoa

Stable Identifier

R-HSA-166721

Type

Reaction [binding]

Species

Homo sapiens

Compartment

extracellular region, plasma membrane

ReviewStatus

5/5

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MBL binds to repetitive carbohydrate structures on the surfaces of viruses, bacteria, fungi, and protozoa

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The MBL polypeptide chain consists of a short N-terminal cysteine-rich region, a collagen-like region comprising 19 Gly-X-Y triplets, a 34-residue hydrophobic stretch, and a C-terminal C-type lectin domain. MBL monomers associate via their cysteine-rich and collagen-like regions to form homotrimers, and these in turn associate into oligomers. The predominant oligomers found in human serum contain three (MBL-I) or four (MBL-II) homotrimers (Fujita et al. 2004, Teillet et al. 2005). Extracellular MBL oligomers circulate as complexes with MASP1/2. In the presence of Ca2+, the carbohydrate recognition domain (CRD) of MBL binds carbohydrates with 3- and 4- OH groups in the pyranose ring, such as mannose and N-acetyl-D-glucosamine. Such motifs occur on the surfaces of viruses, bacteria, fungi and protozoa. The affinity of any one MBL binding site for a carbohydrate ligand is low, but interaction between multiple binding sites on an MBL oligomer and repetitive carbohydrate motifs on a target cell surface allow high-avidity binding. The specificity of the MBL binding site (it does not bind glucose or sialic acid) and the requirement for a repeated target motif may account for the failure of MBL to bind human glycoproteins under normal conditions (Petersen et al. 2001). This reaction in particular represents the interaction of MBL with bacterial mannose repeats.

Literature References

PubMed ID	Title	Journal	Year
11532276	The mannan-binding lectin pathway of complement activation: biology and disease association Petersen, SV, Thiel, S, Jensenius, JC	Mol Immunol	2001
10639434	Mannose-binding lectin binds to a range of clinically relevant microorganisms and promotes complement deposition Neth, O, Jack, DL, Dodds, AW, Holzel, H, Klein, NJ, Turner, MW	Infect Immun	2000
15199963	The lectin-complement pathway--its role in innate immunity and evolution Fujita, T, Matsushita, M, Endo, Y	Immunol Rev	2004
15728497	The two major oligomeric forms of human mannan-binding lectin: chemical characterization, carbohydrate-binding properties, and interaction with MBL-associated serine proteases Teillet, F, Dublet, B, Andrieu, JP, Gaboriaud, C, Arlaud, GJ, Thielens, NM	J Immunol	2005