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1040  structures 260  species 0  interactions 8429  sequences 247  architectures

Family: Lectin_legB (PF00139)

Summary: Legume lectin domain

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This is the Wikipedia entry entitled "Leguminous lectin family". More...

Leguminous lectin family Edit Wikipedia article

PDB 1rin EBI.jpg
x-ray crystal structure of a pea lectin-trimannoside complex at 2.6 angstroms resolution
Symbol Lectin_legB
Pfam PF00139
Pfam clan CL0004
InterPro IPR001220
SCOP 1lem

In molecular biology, the leguminous lectin family is a family of lectin proteins.

It is one of the largest lectin families with more than 70 lectins reported in a review in 1990.[1] Leguminous lectins consist of two or four subunits, each containing one carbohydrate-binding site. The interaction with sugars requires tightly bound calcium and manganese ions. The structural similarities of these lectins are reported by the primary structural analyses and X-ray crystallographic studies.[2][3] X-ray studies have shown that the folding of the polypeptide chains in the region of the carbohydrate-binding sites is also similar, despite differences in the primary sequences. The carbohydrate-binding sites of these lectins consist of two conserved amino acids on beta pleated sheets. One of these loops contains transition metals, calcium and manganese, which keep the amino acid residues of the sugar-binding site at the required positions. Amino acid sequences of this loop play an important role in the carbohydrate-binding specificities of these lectins. These lectins bind either glucose, mannose or galactose. The exact function of legume lectins is not known but they may be involved in the attachment of nitrogen-fixing bacteria to legumes and in the protection against pathogens.[4][5]

Some legume lectins are proteolytically processed to produce two chains, beta (which corresponds to the N-terminal) and alpha (C-terminal). The lectin concanavalin A (conA) from jack bean is exceptional in that the two chains are transposed and ligated (by formation of a new peptide bond). The N terminus of mature conA thus corresponds to that of the alpha chain and the C terminus to the beta chain.[6]


  1. ^ Sharon N, Lis H (1990). "Legume lectins--a large family of homologous proteins.". FASEB J. 4 (14): 3198–208. PMID 2227211. 
  2. ^ de Oliveira TM, Delatorre P, da Rocha BA, de Souza EP, Nascimento KS, Bezerra GA, et al. (2008). "Crystal structure of Dioclea rostrata lectin: insights into understanding the pH-dependent dimer-tetramer equilibrium and the structural basis for carbohydrate recognition in Diocleinae lectins.". J Struct Biol. 164 (2): 177–82. PMID 18682294. doi:10.1016/j.jsb.2008.05.012. 
  3. ^ Rozwarski DA, Swami BM, Brewer CF, Sacchettini JC (1998). "Crystal structure of the lectin from Dioclea grandiflora complexed with core trimannoside of asparagine-linked carbohydrates.". J Biol Chem. 273 (49): 32818–25. PMID 9830028. doi:10.1074/jbc.273.49.32818. 
  4. ^ Roopashree S, Singh SA, Gowda LR, Rao AG (2006). "Dual-function protein in plant defence: seed lectin from Dolichos biflorus (horse gram) exhibits lipoxygenase activity.". Biochem J. 395 (3): 629–39. PMC 1462680Freely accessible. PMID 16441240. doi:10.1042/BJ20051889. 
  5. ^ Beringer JE, Brewin N, Johnston AW, Schulman HM, Hopwood DA (1979). "The Rhizobium--legume symbiosis.". Proc R Soc Lond B Biol Sci. 204 (1155): 219–33. PMID 36624. doi:10.1098/rspb.1979.0024. 
  6. ^ Carrington DM, Auffret A, Hanke DE (1985). "Polypeptide ligation occurs during post-translational modification of concanavalin A.". Nature. 313 (5997): 64–7. PMID 3965973. doi:10.1038/313064a0. 

This article incorporates text from the public domain Pfam and InterPro IPR001220

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This tab holds annotation information from the InterPro database.

InterPro entry IPR001220

Lectins are carbohydrate-binding proteins. Leguminous lectins form one of the largest lectin families and resemble each other in their physicochemical properties, though they differ in their carbohydrate specificities. They bind either glucose/mannose or galactose [ PUBMED:2227211 ]. Carbohydrate-binding activity depends on the simultaneous presence of both a calcium and a transition metal ion [ PUBMED:9546043 ]. The exact function of legume lectins is not known, but they may be involved in the attachment of nitrogen-fixing bacteria to legumes and in the protection against pathogens [ PUBMED:16441240 , PUBMED:36624 ].

Some legume lectins are proteolytically processed to produce two chains, beta (which corresponds to the N-terminal) and alpha (C-terminal) [ PUBMED:8373823 ]. The lectin concanavalin A (conA) from jack bean is exceptional in that the two chains are transposed and ligated (by formation of a new peptide bond). The N terminus of mature conA thus corresponds to that of the alpha chain and the C terminus to the beta chain [ PUBMED:3965973 ]. Though the legume lectins monomer is structurally well conserved, their quaternary structures vary widely [ PUBMED:9546043 ].

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Curation and family details

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Seed source: Prosite
Previous IDs: lectin_legB;
Type: Domain
Sequence Ontology: SO:0000417
Author: Sonnhammer ELL , Bateman A
Number in seed: 78
Number in full: 8429
Average length of the domain: 220.10 aa
Average identity of full alignment: 28 %
Average coverage of the sequence by the domain: 39.01 %

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HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 57096847 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 26.3 26.3
Trusted cut-off 26.3 26.3
Noise cut-off 26.2 26.2
Model length: 249
Family (HMM) version: 21
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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the Lectin_legB domain has been found. There are 1040 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein sequence.

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