Legume Lectin
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{{Infobox protein family , Symbol = Lectin_legB , Name = Legume lectin domain (or L-type lectin domain) , image = PDB 1lem EBI.jpg , width = , caption = Structure of the monosaccharide binding site of lentil lectin.{{cite journal , vauthors=Loris R, Casset F, Bouckaert J, etal , title=The monosaccharide binding site of lentil lectin: an X-ray and molecular modelling study , journal=Glycoconj. J. , volume=11 , issue=6 , pages=507–17 , date=December 1994 , pmid=7696853 , doi= 10.1007/bf00731301, s2cid=20037257 , Pfam = PF00139 , Pfam_clan = CL0004 , InterPro = IPR001220 , SMART = , PROSITE = PDOC00278 , MEROPS = , SCOP = 1lem , TCDB = , OPM family = , OPM protein = , PDB = {{PDB2, 1apn, {{PDB2, 1avb, {{PDB2, 1ax0, {{PDB2, 1ax1, {{PDB2, 1ax2, {{PDB2, 1axy, {{PDB2, 1axz, {{PDB2, 1azd, {{PDB2, 1bjq, {{PDB2, 1bqp, {{PDB2, 1bxh, {{PDB2, 1bzw, {{PDB2, 1ces, {{PDB2, 1ciw, {{PDB2, 1cjp, {{PDB2, 1cn1, {{PDB2, 1con, {{PDB2, 1cq9, {{PDB2, 1cr7, {{PDB2, 1cvn, {{PDB2, 1dbn, {{PDB2, 1dgl, {{PDB2, 1dhk, {{PDB2, 1dq0, {{PDB2, 1dq1, {{PDB2, 1dq2, {{PDB2, 1dq4, {{PDB2, 1dq5, {{PDB2, 1dq6, {{PDB2, 1dzq, {{PDB2, 1enq, {{PDB2, 1enr, {{PDB2, 1ens, {{PDB2, 1f9k, {{PDB2, 1fat, {{PDB2, 1fay, {{PDB2, 1fny, {{PDB2, 1fnz, {{PDB2, 1fx5, {{PDB2, 1fyu, {{PDB2, 1g7y, {{PDB2, 1g8w, {{PDB2, 1g9f, {{PDB2, 1gic, {{PDB2, 1gkb, {{PDB2, 1gnz, {{PDB2, 1gsl, {{PDB2, 1gz9, {{PDB2, 1gzc, {{PDB2, 1h9p, {{PDB2, 1h9w, {{PDB2, 1hkd, {{PDB2, 1hql, {{PDB2, 1hqw, {{PDB2, 1i3h, {{PDB2, 1ioa, {{PDB2, 1jbc, {{PDB2, 1jn2, {{PDB2, 1joj, {{PDB2, 1jui, {{PDB2, 1jw6, {{PDB2, 1jxn, {{PDB2, 1jyc, {{PDB2, 1jyi, {{PDB2, 1lec, {{PDB2, 1led, {{PDB2, 1lem, {{PDB2, 1len, {{PDB2, 1les, {{PDB2, 1lgb, {{PDB2, 1lgc, {{PDB2, 1loa, {{PDB2, 1lob, {{PDB2, 1loc, {{PDB2, 1lod, {{PDB2, 1loe, {{PDB2, 1lof, {{PDB2, 1log, {{PDB2, 1lte, {{PDB2, 1lu1, {{PDB2, 1lu2, {{PDB2, 1lul, {{PDB2, 1mvq, {{PDB2, 1n3o, {{PDB2, 1n3p, {{PDB2, 1n3q, {{PDB2, 1n47, {{PDB2, 1nls, {{PDB2, 1nxd, {{PDB2, 1ofs, {{PDB2, 1ona, {{PDB2, 1q8o, {{PDB2, 1q8p, {{PDB2, 1q8q, {{PDB2, 1q8s, {{PDB2, 1q8v, {{PDB2, 1qdc, {{PDB2, 1qdo, {{PDB2, 1qf3, {{PDB2, 1qgl, {{PDB2, 1qmo, {{PDB2, 1qnw, {{PDB2, 1qny, {{PDB2, 1qoo, {{PDB2, 1qos, {{PDB2, 1qot, {{PDB2, 1rin, {{PDB2, 1rir, {{PDB2, 1rit, {{PDB2, 1s1a, {{PDB2, 1sbd, {{PDB2, 1sbe, {{PDB2, 1sbf, {{PDB2, 1scr, {{PDB2, 1scs, {{PDB2, 1sfy, {{PDB2, 1tei, {{PDB2, 1ukg, {{PDB2, 1uzy, {{PDB2, 1uzz, {{PDB2, 1v00, {{PDB2, 1v6i, {{PDB2, 1v6j, {{PDB2, 1v6k, {{PDB2, 1v6l, {{PDB2, 1v6m, {{PDB2, 1v6n, {{PDB2, 1v6o, {{PDB2, 1val, {{PDB2, 1vam, {{PDB2, 1viw, {{PDB2, 1vln, {{PDB2, 1wbf, {{PDB2, 1wbl, {{PDB2, 1wuv, {{PDB2, 2a7a, {{PDB2, 2ar6, {{PDB2, 2arb, {{PDB2, 2are, {{PDB2, 2arx, {{PDB2, 2auy, {{PDB2, 2b7y, {{PDB2, 2bqp, {{PDB2, 2cna, {{PDB2, 2ctv, {{PDB2, 2cwm, {{PDB2, 2cy6, {{PDB2, 2cyf, {{PDB2, 2d3p, {{PDB2, 2d3r, {{PDB2, 2d3s, {{PDB2, 2d7f, {{PDB2, 2dh1, {{PDB2, 2dtw, {{PDB2, 2dty, {{PDB2, 2du0, {{PDB2, 2du1, {{PDB2, 2dv9, {{PDB2, 2dva, {{PDB2, 2dvb, {{PDB2, 2dvd, {{PDB2, 2dvf, {{PDB2, 2dvg, {{PDB2, 2e51, {{PDB2, 2e53, {{PDB2, 2e7q, {{PDB2, 2e7t, {{PDB2, 2ef6, {{PDB2, 2eig, {{PDB2, 2enr, {{PDB2, 2fmd, {{PDB2, 2g4i, {{PDB2, 2gdf, {{PDB2, 2gme, {{PDB2, 2gmm, {{PDB2, 2gmp, {{PDB2, 2gn3, {{PDB2, 2gn7, {{PDB2, 2gnb, {{PDB2, 2gnd, {{PDB2, 2gnm, {{PDB2, 2gnt, {{PDB2, 2jdz, {{PDB2, 2je7, {{PDB2, 2je9, {{PDB2, 2jec, {{PDB2, 2lal, {{PDB2, 2ltn, {{PDB2, 2ovu, {{PDB2, 2ow4, {{PDB2, 2p2k, {{PDB2, 2p34, {{PDB2, 2p37, {{PDB2, 2pel, {{PDB2, 2phf, {{PDB2, 2phr, {{PDB2, 2pht, {{PDB2, 2phu, {{PDB2, 2phw, {{PDB2, 2phx, {{PDB2, 2sba, {{PDB2, 2tep, {{PDB2, 2uu8, {{PDB2, 2zbj, {{PDB2, 2zmk, {{PDB2, 2zml, {{PDB2, 2zmn, {{PDB2, 3cna, {{PDB2, 3d4k, {{PDB2, 3enr, {{PDB2, 5cna The legume lectins (or L-type lectins) are a family of sugar-binding proteins or
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 ...
s found in the seeds and, in smaller amounts, in the roots, stems, leaves and bark of plants of the family
Fabaceae The Fabaceae or Leguminosae,International Code of Nomenc ...
.{{cite journal , vauthors=Sharon N, Lis H , title=Legume lectins--a large family of homologous proteins , journal=FASEB J. , volume=4 , issue=14 , pages=3198–208 , date=November 1990 , pmid=2227211 , doi= 10.1096/fasebj.4.14.2227211, s2cid=23310019 {{cite journal , vauthors=Loris R, Hamelryck T, Bouckaert J, Wyns L , title=Legume lectin structure , journal=Biochim. Biophys. Acta , volume=1383 , issue=1 , pages=9–36 , date=March 1998 , pmid=9546043 , doi= 10.1016/S0167-4838(97)00182-9 The exact function of the legume lectins ''in vivo'' is unknown but they are probably involved in the defense of plants against predators. Related proteins in other plant families and in animals have also been found. They have been used for decades as a model system for the study of protein-carbohydrate interactions, because they show an amazing variety of binding specificities and are easy to obtain and purify. Over the years, a quite impressive amount of structural data has been gathered. Well-studied members of this protein family include
phytohemagglutinin Phytohaemagglutinin (PHA, or phytohemagglutinin) is a lectin found in plants, especially certain legumes. PHA actually consists of two closely related proteins, called leucoagglutinin (PHA-L) and PHA-E. These proteins cause blood cells to clump ...
and
concanavalin A Concanavalin A (ConA) is a lectin (carbohydrate-binding protein) originally extracted from the jack-bean (''Canavalia ensiformis''). It is a member of the legume lectin family. It binds specifically to certain structures found in various sugars, ...
.


Sugar binding by legume lectins

The legume lectins use an ingenious framework for binding specific sugars. This framework consists of a conserved monosaccharide binding site in which four conserved residues from four separate regions in the protein confer affinity (see figure), a variable loop that confers monosaccharide specificity and a number of subsites around the monosaccharide binding site that harbour additional sugar residues or hydrophobic groups.


Quaternary structure

The legume lectins are also interesting from the point of view of protein structure. Despite the conserved structure of the legume lectin subunit, they can adopt a wide range of quaternary structures.{{cite journal , vauthors=Manoj N, Suguna K , title=Signature of quaternary structure in the sequences of legume lectins , journal=Protein Eng. , volume=14 , issue=10 , pages=735–45 , date=October 2001 , pmid=11739891 , doi= 10.1093/protein/14.10.735, doi-access=free PDBe Browser for legume lectin assemblies
/ref> The reason behind this remarkable variability is probably to be found in the interaction with multivalent ligands.{{cite journal , vauthors=Hamelryck TW, Moore JG, Chrispeels MJ, Loris R, Wyns L , title=The role of weak protein-protein interactions in multivalent lectin-carbohydrate binding: crystal structure of cross-linked FRIL., journal=J. Mol. Biol. , volume=299 , issue=4 , pages=875–83 , date=June 2000 , pmid=10843844 , doi=10.1006/jmbi.2000.3785 {, , - valign=top , ,


References

{{reflist {{Lectins Plant proteins Lectins