PS50231

Lectin domain of ricin B chain profile

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Member databasePROSITE profiles
PROSITE profiles typedomain
Short nameRICIN_B_LECTIN

Description

Primary structure analysis has shown the presence of a similar domain in many carbohydrate-recognition proteins like plant and bacterial AB-toxins, glycosidases or proteases
[3]
[6]
[4]
. This domain, known as the ricin B lectin domain, can be present in one or more copies and has been shown in some instance to bind simple sugars, such as galactose or lactose. The ricin B lectin domain is composed of three homologous subdomains of 40 amino acids (alpha, beta and gamma) and a linker peptide of around 15 residues (lambda). It has been proposed that the ricin B lectin domain arose by gene triplication from a primitive 40 residue galactoside-binding peptide
[5]
[1]
. The most characteristic, though not completely conserved, sequence feature is the presence of a Q-W pattern. Consequently, the ricin B lectin domain as also been refered as the (QxW)3 domain and the three homologous regions as the QxW repeats
[6]
[4]
. A disulfide bond is also conserved in some of the QxW repeats
[6]
. The 3D structure of the ricin B chain has shown that the three QxW repeats pack around a pseudo threefold axis that is stabilised by the lambda linker
[5]
. The ricin B lectin domain has no major segments of a helix or beta sheet but each of the QxW repeats contains an omega loop
[1]
. An idealized omega- loop is a compact, contiguous segment of polypeptide that traces a 'loop- shaped' path in three-dimensional space; the main chain resembles a Greek omega. Some proteins containing a ricin B lectin domain are listed below
[4]
: - Ricin, from Ricinus communis (Castor bean). Ricin belongs to a group of plant AB-toxins, which also contains agglutinin and abrin. Ricin is composed of a sugar-binding subunit (B chain) that attaches to galactose residues presented by cell surface glycoproteins or glycolipids and a subunit (chain A) with enzymatic activity that attacks and inactivates ribosomes. The B chain contains two ricin B lectin domains
[5]
. - Serine protease I (RPI) (EC 3.4.21.-), from Rarobacter faecitabidus
[2]
. RIP is a serine protease exhibiting lytic activity toward living yeast cells. It possess a ricin B lectin domain that is involved in mannose binding in its C terminal part. - The bacterial AHH1/ASH4/HlyA/VVHA family of hemolysins. Bacterial hemolysins are exotoxins that attack blood cell membranes and cause cell rupture by mechanisms not clearly defined. Proteins belonging to this family possess one ricin B lectin domain. - Glucan endo-1,3-beta-glucanase (EC 3.2.1.39), from Oerskovia xanthineolytica. This yeast-lytic protein has a C-terminal ricin B lectin domain which appears to target the catalytic domain to yeast cell wall. - Endo-1,4-beta-xylanase A (EC 3.2.1.8) (gene xlnA), from Streptomyces. The C-terminal ricin B lectin domain has been proposed to bind to the polymeric substrate of this enzyme, but no carbohydrate binding data are available. - The macrophage mannose receptor (MRC1), from mammals. MRC1 is a Type I membrane receptor protein that is expressed at the surface of mature macrophages. It binds mannose- and fucose-rich carbohydrate polymers and appears to mediate phagocytic uptake of foreign microorganisms. Its extracellular region contains 8 copies of the C-type lectin domain and one ricin B lectin domain to which no sugar binding function has been ascribed so far
[7]
. - The AIM1 protein, from mammals. AIM1 is a member of the beta- gamma- crystallin superfamily and contains a C-terminal ricin B lectin domain. In human, it is associated with the control of tumorigenicity. - Phospholipase A2 receptor, from mammals. This proteins contains 8 copies of the C-type lectin domain and one N-terminal ricin B lectin domain whose function is unknown. - UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase (EC 2.4.1.41) (gene GALNT1). This protein catalyzes the initial reaction in O-linked oligosaccharide biosynthesis, the transfer of an N-acetyl-D-galactosamine residue to a serine or threonine residue on the protein receptor. This protein binds carbohydrate as a soluble substrate and contains one copy of the ricin B lectin domain. - The 33-kDa hemagglutinin component of the botulinum neurotoxin complex. This protein has two copies of the ricin B lectin domain and agglutinates red blood cells.

References

1.Structure of ricin B-chain at 2.5 A resolution. Rutenber E, Robertus JD. Proteins 10, 260-9, (1991). View articlePMID: 1881882

2.Molecular structure of Rarobacter faecitabidus protease I. A yeast-lytic serine protease having mannose-binding activity. Shimoi H, Iimura Y, Obata T, Tadenuma M. J. Biol. Chem. 267, 25189-95, (1992). View articlePMID: 1339445

3.Novel galactose-binding proteins in Annelida. Characterization of 29-kDa tandem repeat-type lectins from the earthworm Lumbricus terrestris. Hirabayashi J, Dutta SK, Kasai K. J. Biol. Chem. 273, 14450-60, (1998). View articlePMID: 9603958

4.The (QxW)3 domain: a flexible lectin scaffold. Hazes B. Protein Sci. 5, 1490-501, (1996). View articlePMID: 8844840

5.Structure and evolution of ricin B chain. Rutenber E, Ready M, Robertus JD. Nature 326, 624-6, (1987). View articlePMID: 3561502

6.A mosquitocidal toxin with a ricin-like cell-binding domain. Hazes B, Read RJ. Nat. Struct. Biol. 2, 358-9, (1995). View articlePMID: 7664090

7.The exon-intron structure and chromosomal localization of the mouse macrophage mannose receptor gene Mrc1: identification of a Ricin-like domain at the N-terminus of the receptor. Harris N, Peters LL, Eicher EM, Rits M, Raspberry D, Eichbaum QG, Super M, Ezekowitz RA. Biochem. Biophys. Res. Commun. 198, 682-92, (1994). View articlePMID: 8297379

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