UniProt functional annotation for Q9RHG4



	UniProt functional annotation for Q9RHG4

UniProt code: Q9RHG4.

Organism: Microcystis viridis.

Taxonomy: Bacteria; Cyanobacteria; Oscillatoriophycideae; Chroococcales; Microcystaceae; Microcystis.

Function: Carbohydrate-binding protein that binds oligomannosides such as Man(6)GlcNAc(2) with sub-micromolar affinities. The specificity of MVL is unique in that its minimal target comprises the Man-alpha- (1->6)-Man-beta-(1->4)-GlcNAc-beta-(1->4)-GlcNAc tetrasaccharide core (Man(2)A) found in N-linked oligomannosides. Displays hemagglutininating activity on rabbit, horse and hen erythrocytes. This activity is inhibited by yeast mannan. Does not bind mono- and disaccharides. Inhibits HIV-1 envelope-mediated cell fusion at nanomolar concentrations through carbohydrate-mediated interactions with high-mannose residues on the surface of the HIV envelope glycoprotein gp120.

Function: Unexpectedly for a lectin, one of the 2 oligomannose binding sites of MVL can catalyze the cleavage of chitin fragments (such as chitotriose, i.e. GlcNAc(3) or GlcNAc-beta-(1->4)-GlcNAcbeta-(1->4)- GlcNAc, and chitotetraose, i.e. GlcNAc(4)) to GlcNAc. This weak beta- 1,4-glycosidase activity is restricted to the C-terminal carbohydrate- binding site. Does not cleave Man(3)GlcNAc(2) or the tetrasaccharide Man(2)A. {ECO:0000269|PubMed:19856962}.

Biophysicochemical properties: pH dependence: Displays hemagglutinating activity from pH 5 to 8, but is inactive beyond these pHs. {ECO:0000269|PubMed:10600484}; Temperature dependence: Half the hemagglutinating activity is maintained by heating at 50 degrees Celsius for 3 hours. Is inactive by heating at 60 degrees Celsius for 10 minutes. {ECO:0000269|PubMed:10600484};

Subunit: Homodimer. {ECO:0000269|PubMed:15165858, ECO:0000269|PubMed:15937331, ECO:0000269|PubMed:19856962}.

Subcellular location: Cytoplasm {ECO:0000305|PubMed:10600484}.

Induction: Induced under low nutrient or anoxic conditions. {ECO:0000269|PubMed:10600484}.

Domain: Each monomer contains 2 structurally homologous domains with high sequence similarity connected by a short five-amino acid residue linker. Intriguingly, a water-filled channel is observed between the 2 monomers. {ECO:0000269|PubMed:15937331}.

Miscellaneous: Binds 2 carbohydrate molecules per monomer. The 2 symmetrically related-binding sites exhibit similar affinities relative to one other.

Miscellaneous: The structural studies suggest catalysis likely occurs through proton relay via a 'proton wire'.

Annotations taken from UniProtKB at the EBI.


Organism:		Microcystis viridis.
Taxonomy:		Bacteria; Cyanobacteria; Oscillatoriophycideae; Chroococcales; Microcystaceae; Microcystis.



Function:		Carbohydrate-binding protein that binds oligomannosides such as Man(6)GlcNAc(2) with sub-micromolar affinities. The specificity of MVL is unique in that its minimal target comprises the Man-alpha- (1->6)-Man-beta-(1->4)-GlcNAc-beta-(1->4)-GlcNAc tetrasaccharide core (Man(2)A) found in N-linked oligomannosides. Displays hemagglutininating activity on rabbit, horse and hen erythrocytes. This activity is inhibited by yeast mannan. Does not bind mono- and disaccharides. Inhibits HIV-1 envelope-mediated cell fusion at nanomolar concentrations through carbohydrate-mediated interactions with high-mannose residues on the surface of the HIV envelope glycoprotein gp120.



Function:		Unexpectedly for a lectin, one of the 2 oligomannose binding sites of MVL can catalyze the cleavage of chitin fragments (such as chitotriose, i.e. GlcNAc(3) or GlcNAc-beta-(1->4)-GlcNAcbeta-(1->4)- GlcNAc, and chitotetraose, i.e. GlcNAc(4)) to GlcNAc. This weak beta- 1,4-glycosidase activity is restricted to the C-terminal carbohydrate- binding site. Does not cleave Man(3)GlcNAc(2) or the tetrasaccharide Man(2)A. {ECO:0000269\|PubMed:19856962}.


Biophysicochemical properties:		pH dependence: Displays hemagglutinating activity from pH 5 to 8, but is inactive beyond these pHs. {ECO:0000269\|PubMed:10600484}; Temperature dependence: Half the hemagglutinating activity is maintained by heating at 50 degrees Celsius for 3 hours. Is inactive by heating at 60 degrees Celsius for 10 minutes. {ECO:0000269\|PubMed:10600484};
Subunit:		Homodimer. {ECO:0000269\|PubMed:15165858, ECO:0000269\|PubMed:15937331, ECO:0000269\|PubMed:19856962}.
Subcellular location:		Cytoplasm {ECO:0000305\|PubMed:10600484}.
Induction:		Induced under low nutrient or anoxic conditions. {ECO:0000269\|PubMed:10600484}.
Domain:		Each monomer contains 2 structurally homologous domains with high sequence similarity connected by a short five-amino acid residue linker. Intriguingly, a water-filled channel is observed between the 2 monomers. {ECO:0000269\|PubMed:15937331}.
Miscellaneous:		Binds 2 carbohydrate molecules per monomer. The 2 symmetrically related-binding sites exhibit similar affinities relative to one other.
Miscellaneous:		The structural studies suggest catalysis likely occurs through proton relay via a 'proton wire'.