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Immunobiology. 2002 Sep;205(4-5):455-66.

The mannan-binding lectin-associated serine proteases (MASPs) and MAp19: four components of the lectin pathway activation complex encoded by two genes.

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Department of Microbiology and Immunology, University of Leicester, England, UK.


Mannan-binding lectin (MBL) and ficolins (L-ficolin and H-ficolin) initiate the lectin pathway of complement activation upon binding to microbial carbohydrates. The activation is mediated by associated serine proteases, termed MASPs, since they were discovered as MBL-associated serine proteases. The MASP family comprises three serine proteases, MASP-1, MASP-2 and MASP-3 and a non-enzymatic protein, MAp19. The MASPs show identical domain structure, shared also with C1r and C1s. MASP-1 and MASP-3 are alternative splice products of a single gene, MASP1/3, and have identical A chains, whereas they have individual B chains, encompassing the serine protease domain. MASP2 and MAp19 are alternative splice products of the MASP-2 gene, with MAp19 consisting of the first two domains of MASP-2 plus additional four amino acid residues. MASP-2 is the protease responsible for activating C4 and C2 to generate the C3 convertase, C4bC2b. The biological function of the remaining three proteins has not yet been resolved.

[Indexed for MEDLINE]

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