Leguminous lectin family

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

Lectin_legB
x-ray crystal structure of a pea lectin-trimannoside complex at 2.6 angstroms resolution
Identifiers
SymbolLectin_legB
PfamPF00139
Pfam clanCL0004
InterProIPR001220
PROSITEPDOC00278
SCOP21lem / SCOPe / SUPFAM

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]

References
  1. Sharon N, Lis H (1990). "Legume lectins--a large family of homologous proteins". FASEB J. 4 (14): 3198–208. doi:10.1096/fasebj.4.14.2227211. 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. doi:10.1016/j.jsb.2008.05.012. PMID 18682294.
  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. doi:10.1074/jbc.273.49.32818. PMID 9830028.
  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. doi:10.1042/BJ20051889. PMC 1462680. PMID 16441240.
  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. doi:10.1098/rspb.1979.0024. PMID 36624. S2CID 24965697.
  6. Carrington DM, Auffret A, Hanke DE (1985). "Polypeptide ligation occurs during post-translational modification of concanavalin A.". Nature. 313 (5997): 64–7. doi:10.1038/313064a0. PMID 3965973. S2CID 4359482.
This article incorporates text from the public domain Pfam and InterPro: IPR001220
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