Summary: Legume lectin domain

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

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Leguminous lectin family Edit Wikipedia article

Lectin_legB

x-ray crystal structure of a pea lectin-trimannoside complex at 2.6 angstroms resolution

Identifiers

Symbol

Lectin_legB

Pfam clan

Available protein structures:
Pfam	structures
PDB	RCSB PDB; PDBe; PDBj
PDBsum	structure summary

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]

References

^ Sharon N, Lis H (1990). "Legume lectins--a large family of homologous proteins.". FASEB J. 4 (14): 3198–208. PMID 2227211.
^ 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.
^ 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.
^ 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.
^ 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.
^ 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.

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

This page is based on a Wikipedia article. The text is available under the Creative Commons Attribution/Share-Alike License.

This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.

Legume lectin domain Provide feedback

No Pfam abstract.

Internal database links

SCOOP:	Lectin_leg-like
Similarity to PfamA using HHSearch:	Lectin_leg-like

External database links

HOMSTRAD:	ltn
PROSITE:	PDOC00278
SCOP:	1lem

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].

Gene Ontology

The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.

Molecular function

carbohydrate binding (GO:0030246)

Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

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Pfam Clan

This family is a member of clan Concanavalin (CL0004), which has the following description:

This superfamily includes a diverse range of carbohydrate binding domains and glycosyl hydrolase enzymes that share a common structure.

The clan contains the following 43 members:

Alginate_lyase2 ArabFuran-catal Bac_rhamnosid Calreticulin Cleaved_Adhesin DUF1080 DUF1349 DUF1583 DUF1961 DUF2401 DUF3472 DUF4975 Exotox-A_bind Gal-bind_lectin Glyco_hydro_11 Glyco_hydro_12 Glyco_hydro_16 Glyco_hydro_32C Glyco_hydro_7 Laminin_G_1 Laminin_G_2 Laminin_G_3 Lectin_leg-like Lectin_legB MAM Methyltransf_FA Neuralized Pentaxin Peptidase_A4 Polysacc_lyase PRY Reoviridae_Vp9 Sial-lect-inser Sialidase SKN1 Spike_NTD SPRY TgMIC1 Toxin_R_bind_N TSP_C VP4_haemagglut XET_C YrpD

Alignments

We store a range of different sequence alignments for families. As well as the seed alignment from which the family is built, we provide the full alignment, generated by searching the sequence database (reference proteomes) using the family HMM. We also generate alignments using four representative proteomes (RP) sets, the UniProtKB sequence database, the NCBI sequence database, and our metagenomics sequence database. More...

There are various ways to view or download the sequence alignments that we store. We provide several sequence viewers and a plain-text Stockholm-format file for download.

Alignment types

We make a range of alignments for each Pfam-A family:

seed: the curated alignment from which the HMM for the family is built
full: the alignment generated by searching the sequence database using the HMM
RP15/RP35/RP55/RP75: Representative Proteomes (RPs) at 15%, 35%, 55% and 75% co-membership thresholds
UniProt: alignment generated by searching the UniProtKB sequence database using the family HMM
NCBI: alignment generated by searching the NCBI sequence database using the family HMM
meta: alignment generated by searching the metagenomics sequence database using the family HMM

Viewing

You can see the alignments as HTML or in three different sequence viewers:

jalview: a Java applet developed at the University of Dundee. You will need Java installed before running jalview
HTML: an HTML page showing the whole alignment.Please note: full Pfam alignments can be very large. These HTML views are extremely large and often cause problems for browsers. Please use either jalview or the Pfam viewer if you have trouble viewing the HTML version
PP/Heatmap: an HTML-based representation of the alignment, coloured according to the posterior-probability (PP) values from the HMM. As for the standard HTML view, heatmap alignments can also be very large and slow to render.

Reformatting

You can download (or view in your browser) a text representation of a Pfam alignment in various formats:

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Stockholm
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You can also change the order in which sequences are listed in the alignment, change how insertions are represented, alter the characters that are used to represent gaps in sequences and, finally, choose whether to download the alignment or to view it in your browser directly.

Downloading

You may find that large alignments cause problems for the viewers and the reformatting tool, so we also provide all alignments in Stockholm format. You can download either the plain text alignment, or a gzipped version of it.

View options

We make a range of alignments for each Pfam-A family. You can see a description of each above. You can view these alignments in various ways but please note that some types of alignment are never generated while others may not be available for all families, most commonly because the alignments are too large to handle.

	Seed (94)	Full (3578)	Representative proteomes				UniProt (5080)	NCBI (7171)	Meta (44)
	Seed (94)	Full (3578)	RP15 (278)	RP35 (1710)	RP55 (3127)	RP75 (3754)	UniProt (5080)	NCBI (7171)	Meta (44)
Jalview	View	View	View	View	View	View	View	View	View
HTML	View	View
PP/heatmap	₁	View

¹Cannot generate PP/Heatmap alignments for seeds; no PP data available

Key: available, not generated, — not available.

Format an alignment

	Seed (94)	Full (3578)	Representative proteomes				UniProt (5080)	NCBI (7171)	Meta (44)
	Seed (94)	Full (3578)	RP15 (278)	RP35 (1710)	RP55 (3127)	RP75 (3754)	UniProt (5080)	NCBI (7171)	Meta (44)
Alignment:
Format:
Order:	Tree Alphabetical
Sequence:	Inserts lower case All upper case
Gaps:
Download/view:	Download View

Download options

We make all of our alignments available in Stockholm format. You can download them here as raw, plain text files or as gzip-compressed files.

	Seed (94)	Full (3578)	Representative proteomes				UniProt (5080)	NCBI (7171)	Meta (44)
	Seed (94)	Full (3578)	RP15 (278)	RP35 (1710)	RP55 (3127)	RP75 (3754)	UniProt (5080)	NCBI (7171)	Meta (44)
Raw Stockholm	Download	Download	Download	Download	Download	Download	Download	Download	Download
Gzipped	Download	Download	Download	Download	Download	Download	Download	Download	Download

You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

HMM logo

HMM logos is one way of visualising profile HMMs. Logos provide a quick overview of the properties of an HMM in a graphical form. You can see a more detailed description of HMM logos and find out how you can interpret them here. More...

Trees

This page displays the phylogenetic tree for this family's seed alignment. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed alignment.

Note: You can also download the data file for the tree.

Curation and family details

This section shows the detailed information about the Pfam family. You can see the definitions of many of the terms in this section in the glossary and a fuller explanation of the scoring system that we use in the scores section of the help pages.

Curation

Seed source:

Prosite

Previous IDs:

lectin_legB;

Type:

Domain

Author:

Sonnhammer ELL, Bateman A

Number in seed:

94

Number in full:

3578

Average length of the domain:

219.20 aa

Average identity of full alignment:

28 %

Average coverage of the sequence by the domain:

39.57 %

HMM information

HMM build commands:

build method: hmmbuild -o /dev/null HMM SEED

search method: hmmsearch -Z 26740544 -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:

250

Family (HMM) version:

18

Download:

download the raw HMM for this family

Species distribution

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Colour assignments

Archea	Eukaryota
Bacteria	Other sequences
Viruses	Unclassified
Viroids	Unclassified sequence

Selections

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This visualisation provides a simple graphical representation of the distribution of this family across species. You can find the original interactive tree in the adjacent tab. More...

This chart is a modified "sunburst" visualisation of the species tree for this family. It shows each node in the tree as a separate arc, arranged radially with the superkingdoms at the centre and the species arrayed around the outermost ring.

How the sunburst is generated

The tree is built by considering the taxonomic lineage of each sequence that has a match to this family. For each node in the resulting tree, we draw an arc in the sunburst. The radius of the arc, its distance from the root node at the centre of the sunburst, shows the taxonomic level ("superkingdom", "kingdom", etc). The length of the arc represents either the number of sequences represented at a given level, or the number of species that are found beneath the node in the tree. The weighting scheme can be changed using the sunburst controls.

In order to reduce the complexity of the representation, we reduce the number of taxonomic levels that we show. We consider only the following eight major taxonomic levels:

superkingdom
kingdom
phylum
class
order
family
genus
species

Colouring and labels

Segments of the tree are coloured approximately according to their superkingdom. For example, archeal branches are coloured with shades of orange, eukaryotes in shades of purple, etc. The colour assignments are shown under the sunburst controls. Where space allows, the name of the taxonomic level will be written on the arc itself.

As you move your mouse across the sunburst, the current node will be highlighted. In the top section of the controls panel we show a summary of the lineage of the currently highlighed node. If you pause over an arc, a tooltip will be shown, giving the name of the taxonomic level in the title and a summary of the number of sequences and species below that node in the tree.

Anomalies in the taxonomy tree

There are some situations that the sunburst tree cannot easily handle and for which we have work-arounds in place.

Missing taxonomic levels

Some species in the taxonomic tree may not have one or more of the main eight levels that we display. For example, Bos taurus is not assigned an order in the NCBI taxonomic tree. In such cases we mark the omitted level with, for example, "No order", in both the tooltip and the lineage summary.

Unmapped species names

The tree is built by looking at each sequence in the full alignment for the family. We take the name of the species given by UniProt and try to map that to the full taxonomic tree from NCBI. In some cases, the name chosen by UniProt does not map to any node in the NCBI tree, perhaps because the chosen name is listed as a synonym or a misspelling in the NCBI taxonomy.

So that these nodes are not simply omitted from the sunburst tree, we group them together in a separate branch (or segment of the sunburst tree). Since we cannot determine the lineage for these unmapped species, we show all levels between the superkingdom and the species as "uncategorised".

Sub-species

Since we reduce the species tree to only the eight main taxonomic levels, sequences that are mapped to the sub-species level in the tree would not normally be shown. Rather than leave out these species, we map them instead to their parent species. So, for example, for sequences belonging to one of the Vibrio cholerae sub-species in the NCBI taxonomy, we show them instead as belonging to the species Vibrio cholerae.

Too many species/sequences

For large species trees, you may see blank regions in the outer layers of the sunburst. These occur when there are large numbers of arcs to be drawn in a small space. If an arc is less than approximately one pixel wide, it will not be drawn and the space will be left blank. You may still be able to get some information about the species in that region by moving your mouse across the area, but since each arc will be very small, it will be difficult to accurately locate a particular species.

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Tree controls

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The tree shows the occurrence of this domain across different species. More...

Species trees

We show the species tree in one of two ways. For smaller trees we try to show an interactive representation, which allows you to select specific nodes in the tree and view them as an alignment or as a set of Pfam domain graphics.

Unfortunately we have found that there are problems viewing the interactive tree when the it becomes larger than a certain limit. Furthermore, we have found that Internet Explorer can become unresponsive when viewing some trees, regardless of their size. We therefore show a text representation of the species tree when the size is above a certain limit or if you are using Internet Explorer to view the site.

If you are using IE you can still load the interactive tree by clicking the "Generate interactive tree" button, but please be aware of the potential problems that the interactive species tree can cause.

Interactive tree

For all of the domain matches in a full alignment, we count the number that are found on all sequences in the alignment. This total is shown in the purple box.

We also count the number of unique sequences on which each domain is found, which is shown in green. Note that a domain may appear multiple times on the same sequence, leading to the difference between these two numbers.

Finally, we group sequences from the same organism according to the NCBI code that is assigned by UniProt, allowing us to count the number of distinct sequences on which the domain is found. This value is shown in the pink boxes.

We use the NCBI species tree to group organisms according to their taxonomy and this forms the structure of the displayed tree. Note that in some cases the trees are too large (have too many nodes) to allow us to build an interactive tree, but in most cases you can still view the tree in a plain text, non-interactive representation. Those species which are represented in the seed alignment for this domain are highlighted.

You can use the tree controls to manipulate how the interactive tree is displayed:

show/hide the summary boxes
highlight species that are represented in the seed alignment
expand/collapse the tree or expand it to a given depth
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Interactions

There are 3 interactions for this family. More...

Transferrin Lectin_legB Alpha-amylase

Structures

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 889 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 seqence.

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Family: Lectin_legB (PF00139)

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