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1dqg A: PDB entry domain

SCOP classification
Root:   SCOP hierarchy in SUPERFAMILY [ 0] (11)
Class:   All beta proteins [ 48724] (174)
Fold:   beta-Trefoil [ 50352] (8)
Superfamily:   Ricin B-like lectins [ 50370] (3)
Family:   Cysteine rich domain [ 50379]
Protein:   Mannose receptor [50380]
PDB Entry Domain:   1dqg A: [ 25579]
  SUPERFAMILY domain annotation for 1dqga
  PDB structure summary for 1dqg

InterPro annotation
Cross references IPR008997 SSF50370 Protein matches

The plant cytotoxin ricin is a heterodimer. The A chain, known to be a specific N-glycosidase, has a prominent active site cleft. The B chain is a two-domain lectin, which arose from the replication of a primitive sugar binding peptide. The B chain subunit of ricin (RTB)1 binds to mammalian cell membranes by recognizing galactose-containing receptors. RTB has two domains each with three subdomains; tripeptide kinks in the loops from subdomains 1alpha, 1beta, 2alpha, and 2gamma may interact with galactosides. Each of these subdomains has aromatic residues that can interact with the nonpolar face of galactose, and three of the four subdomain folds (1alpha, 1beta, and 2gamma) have polar residues for hydrogen bond formation to the sugar hydroxyls [PubMed8950484].

The family 10 xylanase from Streptomyces olivaceoviridis E-86 contains a (beta/alpha)(8)-barrel as a catalytic domain, a family 13 carbohydrate binding module as a xylan binding domain (XBD) and a Gly/Pro-rich linker between them. The crystal structure of this enzyme showed that XBD has three similar subdomains, as indicated by the presence of a triple-repeated sequence, forming a galactose binding lectin fold similar to that found in the ricin toxin B-chain [PubMed11829503].

InterPro database

PDBeMotif information about ligands, sequence and structure motifs
Cross references PDB entries
Ligand binding statistics
Nucleic-acid binding statistics
Occurrence of secondary structure elements
Occurrence of small 3D structural motifs

PDBeMotif resource

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Internal database links

Superfamily level     Family level

Browse genome assignments for this superfamily. The SUPERFAMILY hidden Markov model library has been used to carry out SCOP domain assignments to all genomes at the superfamily level.

Superfamily level     Family level

Alignments of sequences to 48 models in this superfamily are available by clicking on the 'Alignments' icon above. PDB sequences less than 40% identical are shown by default, but any other sequence(s) may be aligned. Select PDB sequences, genome sequences, or paste in or upload your own sequences.

Superfamily level

Browse and view proteins in genomes which have different domain combinations including a Ricin B-like lectins domain.

Superfamily level     Family level

Examine the distribution of domain superfamilies, or families, across the major taxonomic kingdoms or genomes within a kingdom. This gives an immediate impression of how superfamilies, or families, are restricted to certain kingdoms of life.

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