Mannan-binding lectin serine protease 2 also known as mannose-binding protein-associated serine protease 2 (MASP-2) is an
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
that in humans is encoded by the ''MASP2''
gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
.
Function
The Ra-reactive factor (RARF) is a complement-dependent bactericidal factor that binds to the Ra and R2
polysaccharide
Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wa ...
s expressed by certain
enterobacteria
Enterobacteriaceae is a large family of Gram-negative bacteria
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their ...
. Alternate splicing of this gene results in two transcript variants encoding two RARF components that are involved in the
mannan-binding
lectin
Lectins are carbohydrate-binding proteins that are highly specific for sugar groups that are part of other molecules, so cause agglutination of particular cells or precipitation of glycoconjugates and polysaccharides. Lectins have a role in rec ...
pathway of
complement activation
The complement system, also known as complement cascade, is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic
Phagocytosis () is the process by which a cell uses its plasma membrane to engulf a ...
. The longer isoform is cleaved into two chains which form a heterodimer linked by a
disulfide bond
In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In ...
. The encoded proteins are members of the
trypsin
Trypsin is an enzyme in the first section of the small intestine that starts the digestion of protein molecules by cutting these long chains of amino acids into smaller pieces. It is a serine protease from the PA clan superfamily, found in the dig ...
family of peptidases.
MASP-2 is involved in the
complement system
The complement system, also known as complement cascade, is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and at ...
. MASP-2 is very similar to the C1s molecule, of the classical complement pathway, and they are thought to have a common evolutionary ancestor. When the carbohydrate-recognising heads of MBL bind to specifically arranged mannose residues on the surface of a pathogen, MASP-2 is activated to cleave complement components C4 and C2 into C4a, C4b, C2a, and C2b.
See also
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MASP1 (protein)
Mannan-binding lectin serine protease 1 also known as mannose-associated serine protease 1 (MASP-1) is an enzyme that in humans is encoded by the ''MASP1'' gene.
MASP-1 is involved in the lectin pathway of the complement system and is responsible ...
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Mannan-binding lectin
Mannose-binding lectin (MBL), also called mannan-binding lectin or mannan-binding protein (MBP), is a lectin that is instrumental in innate immunity as an opsonin and via the lectin pathway.
Structure
MBL has an oligomeric structure (400-700 kDa) ...
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Mannan-binding lectin pathway
The lectin pathway or lectin complement pathway is a type of cascade reaction in the complement system, similar in structure to the classical complement pathway, in that, after activation, it proceeds through the action of C4 and C2 to produce acti ...
(lectin pathway)
References
Further reading
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External links
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Complement system
EC 3.4.21