UCSD Molecule Pages
Published online: 15 May 2013 | doi:10.6072/H0.MP.A004266.01
Basis Sequence: Human
Anjana Chandrasekhar1, Ashok Reddy Dinasarapu1, Steffen Thiel2, Shankar Subramaniam3
1Department of Bioengineering, University of California, San Diego, CA 92093, US. 2Department of Biomedicine, Aarhus University, 8000, DK. 3Department of Bioengineering, University of California at San Diego, CA 92093, US.
Correspondence should be addressed to Anjana Chandrasekhar: firstname.lastname@example.org
L-ficolin is a serum lectin synthesized (as a ~37 kDa polypeptide) predominantly by the liver, and is one of the key molecules of the innate immune system. It has an amino (N)-terminal cysteine-rich region, a middle stretch of a collagen-like sequence, and a fibrinogen-like domain in the carboxy (C)-terminus. Three identical polypeptides form a structural (triple helical) subunit, with the help of the collagen-like domain. Further oligomerization of this subunit results in different sized L-ficolin molecules (from dimers to tetramers) in circulation. However, the tetrameric form (composed of 12 polypeptides) is the most prevalent structure. The polypeptides in the structural subunit are cross-linked by disulphide bonds in the N-terminal region. The fibrinogen-like domain forms a globular structure. The overall structure of oligomeric L-ficolin closely resembles mannose-binding lectin (MBL). Similar to MBL, L-ficolin also acts as a pattern recognition receptor. It primarily recognizes acetylated sugar residues on the cell surface of different gram-positive and gram-negative bacteria, viruses and other pathogens. There are two pathways by which L-ficolin may participate in a host defense response: 1) It activates the complement lectin pathway, via MBL/ficolin associated serine proteases (MASPs), that converges with the classical complement pathway at the level of complement C4, and 2) it may also act directly as an opsonin, enhancing phagocytosis by binding to cell-surface receptors present on phagocytic cells. M-ficolin and H-ficolin are structurally similar to L-ficolin. However, they differ in their tissue expression and binding affinities to pathogenic ligands.
Alternative names for this molecule:
37 kDa elastin-binding protein; Collagen/fibrinogen domain-containing protein 2; EBP-37; FCN2; FCNL; Ficolin (collagen/fibrinogen domain containing lectin) 2 (hucolin); Ficolin B; Ficolin-2; ficolin-2; Ficolin-B; Ficolin-beta; Hucolin; L-ficolin; L-Ficolin; P35; Serum lectin p35
The UCSD Signaling Gateway Molecule Pages (SGMP) is funded by NIH/NIGMS Grant 1 R01 GM078005-01. The authors thank Dr. John D. Lambris, University of Pennsylvania, Philadelphia, UCSD-SGMP editorial board member, for extensive discussions.