The mannan-binding lectin-associated serine proteases (MASPs) and MAp19: four components of the lectin pathway activation complex encoded by two genes.
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.
Schwaeble
Wilhelm
W
Department of Microbiology and Immunology, University of Leicester, England, UK. ws5@leicester.ac.uk
Dahl
Mads R
MR
Thiel
Steffen
S
Stover
Cordula
C
Jensenius
Jens C
JC
D000818:Animals; D003167:Complement Activation / Q000235:genetics / Q000502:physiology; D037582:Complement Pathway, Mannose-Binding Lectin / Q000235:genetics* / Q000502:physiology; D006801:Humans; D050606:Mannose-Binding Protein-Associated Serine Proteases; D010802:Phylogeny; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism
C105296:MASP2 protein, human; D050606:Mannose-Binding Protein-Associated Serine Proteases; D012697:Serine Endopeptidases