Leguminous lectin family

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Lectin_legB
PDB 1rin EBI.jpg
x-ray crystal structure of a pea lectin-trimannoside complex at 2.6 angstroms resolution
Identifiers
SymbolLectin_legB
Pfam PF00139
Pfam clan CL0004
InterPro IPR001220
PROSITE PDOC00278
SCOP2 1lem / SCOPe / SUPFAM

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]

Related Research Articles

Lectin Carbohydrate-binding protein

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 recognition at the cellular and molecular level and play numerous roles in biological recognition phenomena involving cells, carbohydrates, and proteins. Lectins also mediate attachment and binding of bacteria, viruses, and fungi to their intended targets.

An oligosaccharide is a saccharide polymer containing a small number of monosaccharides. Oligosaccharides can have many functions including cell recognition and cell binding. For example, glycolipids have an important role in the immune response.

Concanavalin A Lectin (carbohydrate-binding protein) originally extracted from the jack-bean

Concanavalin A (ConA) is a lectin originally extracted from the jack-bean. It is a member of the legume lectin family. It binds specifically to certain structures found in various sugars, glycoproteins, and glycolipids, mainly internal and nonreducing terminal α-D-mannosyl and α-D-glucosyl groups. ConA is a plant mitogen, and is known for its ability to stimulate mouse T-cell subsets giving rise to four functionally distinct T cell populations, including precursors to regulatory T cells; a subset of human suppressor T-cells is also sensitive to ConA. ConA was the first lectin to be available on a commercial basis, and is widely used in biology and biochemistry to characterize glycoproteins and other sugar-containing entities on the surface of various cells. It is also used to purify glycosylated macromolecules in lectin affinity chromatography, as well as to study immune regulation by various immune cells.

Major basic protein

Eosinophil major basic protein, often shortened to major basic protein is encoded in humans by the PRG2 gene.

EF-Tu Prokaryotic elongation factor

EF-Tu is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome. It is a G-protein, and facilitates the selection and binding of an aa-tRNA to the A-site of the ribosome. As a reflection of its crucial role in translation, EF-Tu is one of the most abundant and highly conserved proteins in prokaryotes. It is found in eukaryotic mitochrondria as TUFM.

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.

Thermolysin

Thermolysin is a thermostable neutral metalloproteinase enzyme produced by the Gram-positive bacteria Bacillus thermoproteolyticus. It requires one zinc ion for enzyme activity and four calcium ions for structural stability. Thermolysin specifically catalyzes the hydrolysis of peptide bonds containing hydrophobic amino acids. However thermolysin is also widely used for peptide bond formation through the reverse reaction of hydrolysis. Thermolysin is the most stable member of a family of metalloproteinases produced by various Bacillus species. These enzymes are also termed 'neutral' proteinases or thermolysin -like proteinases (TLPs).

Galectin-1

Galectin-1 is a protein that in humans is encoded by the LGALS1 gene.

GP1BA

Platelet glycoprotein Ib alpha chain also known as glycoprotein Ib (platelet), alpha polypeptide or CD42b, is a protein that in humans is encoded by the GP1BA gene.

EGF-like domain Protein domain named after the epidermal growth factor protein

The EGF-like domain is an evolutionary conserved protein domain, which derives its name from the epidermal growth factor where it was first described. It comprises about 30 to 40 amino-acid residues and has been found in a large number of mostly animal proteins. Most occurrences of the EGF-like domain are found in the extracellular domain of membrane-bound proteins or in proteins known to be secreted. An exception to this is the prostaglandin-endoperoxide synthase. The EGF-like domain includes 6 cysteine residues which in the epidermal growth factor have been shown to form 3 disulfide bonds. The structures of 4-disulfide EGF-domains have been solved from the laminin and integrin proteins. The main structure of EGF-like domains is a two-stranded β-sheet followed by a loop to a short C-terminal, two-stranded β-sheet. These two β-sheets are usually denoted as the major (N-terminal) and minor (C-terminal) sheets. EGF-like domains frequently occur in numerous tandem copies in proteins: these repeats typically fold together to form a single, linear solenoid domain block as a functional unit.

GP1BB

Glycoprotein Ib (platelet), beta polypeptide (GP1BB) also known as CD42c, is a protein that in humans is encoded by the GP1BB gene.

FBLN2

Fibulin-2 is a protein that in humans is encoded by the FBLN2 gene.

Legume lectin

The legume lectins are a family of sugar-binding proteins or lectins found in the seeds and, in smaller amounts, in the roots, stems, leaves and bark of plants of the family Fabaceae. 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 and concanavalin A.

The Walker A and Walker B motifs are protein sequence motifs, known to have highly conserved three-dimensional structures. These were first reported in ATP-binding proteins by Walker and co-workers in 1982.

Mamannamana Vijayan is an Indian structural biologist. His main area of research is protein structures. His contributions have been towards the structure and carbohydrate specificity of lectins and protein hydration. He has also contributed towards the area of structure and interactions of mycobacterial proteins and supramolecular association with reference to chemical evolution and origin of life. Vijayan did biological macromolecular crystallography in India.

Circular permutation in proteins Arrangement of amino acid sequence

A circular permutation is a relationship between proteins whereby the proteins have a changed order of amino acids in their peptide sequence. The result is a protein structure with different connectivity, but overall similar three-dimensional (3D) shape. In 1979, the first pair of circularly permuted proteins – concanavalin A and lectin – were discovered; over 2000 such proteins are now known.

Carbohydrate-binding module

In molecular biology, a carbohydrate-binding module (CBM) is a protein domain found in carbohydrate-active enzymes. The majority of these domains have carbohydrate-binding activity. Some of these domains are found on cellulosomal scaffoldin proteins. CBMs were previously known as cellulose-binding domains. CBMs are classified into numerous families, based on amino acid sequence similarity. There are currently 64 families of CBM in the CAZy database.

In molecular biology, the galactose binding lectin domain is a protein domain. It is found in many proteins including the lectin purified from sea urchin eggs, SUEL. This lectin exists as a disulfide-linked homodimer of two subunits; the dimeric form is essential for hemagglutination activity. The sea urchin egg lectin (SUEL) forms a new class of lectins. Although SUEL was first isolated as a D-galactoside binding lectin, it was later shown that it binds to L-rhamnose preferentially. L-rhamnose and D-galactose share the same hydroxyl group orientation at C2 and C4 of the pyranose ring structure.

L-type lectin domain

In molecular biology the L-like lectin domain is a protein domain found in lectins which are similar to the leguminous plant lectins.

Intelectin

Intelectins are lectins expressed in humans and other chordates. Humans express two types of intelectins encoded by ITLN1 and ITLN2 genes respectively. Several intelectins bind microbe-specific carbohydrate residues. Therefore, intelectins have been proposed to function as immune lectins. Even though intelectins contain fibrinogen-like domain found in the ficolins family of immune lectins, there is significant structural divergence. Thus, intelectins may not function through the same lectin-complement pathway. Most intelectins are still poorly characterized and they may have diverse biological roles. Human intelectin-1 (hIntL-1) has also been shown to bind lactoferrin, but the functional consequence has yet to be elucidated. Additionally, hIntL-1 is a major component of asthmatic mucus and may be involved in insulin physiology as well.

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. S2CID   23310019.
  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