Mannose- or mannan-binding lectin (MBL) is a member of the collectin protein family, which includes lung surfactant proteins SP-A and SP-D. Each member consists of similar or identical polypeptide chains with a region of collagen-like sequence followed by a C-type lectin domain. The polypeptides associate in threes to form a subunit containing a collagen-like helix, with three clustered lectin domains. These subunits associate into larger structures, usually with 12–18 polypeptides. The collectins bind to patterns of neutral sugars on surfaces (e.g. of micro-organisms) and mediate effector functions associated with killing/phagocytosis. MBL is the only collectin which activates complement. It resembles in quaternary structure the complement protein C1q, which recognizes targets via charge clusters. Binding of MBL to a surface activates MBL-associated serine proteases (MASPs) attached to MBL, and MASP-2 activates complement proteins C4 and C2. The MASPs are homologous to the C1q-associated proteases, C1r and C1s. MBL therefore activates complement by a mechanism very similar to C1q, and engages the opsonic activity of complement to clear micro-organisms. The serum concentration of MBL is very variable in humans. The variability is largely associated with mutations leading to amino acid substitutions in the collagen-like region which decrease MBL assembly and stability. Many studies demonstrate that MBL deficiency is associated with susceptibility to a range of infectious and inflammatory diseases.
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August 2003
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Conference Article|
August 01 2003
Biochemistry and genetics of mannan-binding lectin (MBL)
J.S. Presanis;
J.S. Presanis
MRC Immunochemistry Unit, Department of Biochemistry, Oxford University, South Parks Road, Oxford OX1 3QU, U.K.
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M. Kojima;
M. Kojima
MRC Immunochemistry Unit, Department of Biochemistry, Oxford University, South Parks Road, Oxford OX1 3QU, U.K.
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R.B. Sim
R.B. Sim
1
MRC Immunochemistry Unit, Department of Biochemistry, Oxford University, South Parks Road, Oxford OX1 3QU, U.K.
1To whom correspondence should be addressed (e-mail bob.sim@bioch.ox.ac.uk).
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Publisher: Portland Press Ltd
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© 2003 Biochemical Society
2003
Biochem Soc Trans (2003) 31 (4): 748–752.
Citation
J.S. Presanis, M. Kojima, R.B. Sim; Biochemistry and genetics of mannan-binding lectin (MBL). Biochem Soc Trans 1 August 2003; 31 (4): 748–752. doi: https://doi.org/10.1042/bst0310748
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