| Structural highlights
1pum is a 2 chain structure with sequence from Viscum album. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
| | Ligands: | , , , , , , |
| Related: | 1puu |
| Resources: | FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT |
Function
[ML1_VISAL] The A chain is responsible for inhibiting protein synthesis through the catalytic inactivation of 60S ribosomal subunits by removing adenine from position 4,324 of 28S rRNA. The B chain binds to cell receptors and probably facilitates the entry into the cell of the A chain; B chains are also responsible for cell agglutination (lectin activity). Inhibits growth of the human tumor cell line Molt4.[1] [2] [3]
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
The structures of mistletoe lectin I (ML-I) from Viscum album complexed with lactose and galactose have been determined at 2.3 A resolution and refined to R factors of 20.9% (Rfree = 23.6%) and 20.9 (Rfree = 24.6%), respectively. ML-I is a heterodimer and belongs to the class of ribosome-inactivating proteins of type II, which consist of two chains. The A-chain has rRNA N-glycosidase activity and irreversibly inhibits eukaryotic ribosomes. The B-chain is a lectin and preferentially binds to galactose-terminated glycolipids and glycoproteins on cell membranes. Saccharide binding is performed by two binding sites in subdomains alpha1 and gamma2 of the ML-I B-chain separated by approximately 62 A from each other. The favoured binding of galactose in subdomain alpha1 is achieved via hydrogen bonds connecting the 4-hydroxyl and 3-hydroxyl groups of the sugar moiety with the side chains of Asp23B, Gln36B and Lys41B and the main chain of 26B. The aromatic ring of Trp38B on top of the preferred binding pocket supports van der Waals packing of the apolar face of galactose and stabilizes the sugar-lectin complex. In the galactose-binding site II of subdomain gamma2, Tyr249B provides the hydrophobic stacking and the side chains of Asp235B, Gln238B and Asn256B are hydrogen-bonding partners for galactose. In the case of the galactose-binding site I, the 2-hydroxyl group also stabilizes the sugar-protein complex, an interaction thus far rarely detected in galactose-specific lectins. Finally, a potential third low-affinity galactose-binding site in subunit beta1 was identified in the present ML-I structures, in which a glycerol molecule from the cryoprotectant buffer has bound, mimicking the sugar compound.
Mistletoe lectin I in complex with galactose and lactose reveals distinct sugar-binding properties.,Mikeska R, Wacker R, Arni R, Singh TP, Mikhailov A, Gabdoulkhakov A, Voelter W, Betzel C Acta Crystallogr Sect F Struct Biol Cryst Commun. 2005 Jan 1;61(Pt, 1):17-25. Epub 2004 Dec 24. PMID:16508080[4]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Kourmanova AG, Soudarkina OJ, Olsnes S, Kozlov JV. Cloning and characterization of the genes encoding toxic lectins in mistletoe (Viscum album L). Eur J Biochem. 2004 Jun;271(12):2350-60. PMID:15182350 doi:http://dx.doi.org/10.1111/j.1432-1033.2004.04153.x
- ↑ Mishra V, Sharma RS, Yadav S, Babu CR, Singh TP. Purification and characterization of four isoforms of Himalayan mistletoe ribosome-inactivating protein from Viscum album having unique sugar affinity. Arch Biochem Biophys. 2004 Mar 15;423(2):288-301. PMID:15001393 doi:http://dx.doi.org/10.1016/j.abb.2003.12.033
- ↑ Dietrich JB, Ribereau-Gayon G, Jung ML, Franz H, Beck JP, Anton R. Identity of the N-terminal sequences of the three A chains of mistletoe (Viscum album L.) lectins: homology with ricin-like plant toxins and single-chain ribosome-inhibiting proteins. Anticancer Drugs. 1992 Oct;3(5):507-11. PMID:1450445
- ↑ Mikeska R, Wacker R, Arni R, Singh TP, Mikhailov A, Gabdoulkhakov A, Voelter W, Betzel C. Mistletoe lectin I in complex with galactose and lactose reveals distinct sugar-binding properties. Acta Crystallogr Sect F Struct Biol Cryst Commun. 2005 Jan 1;61(Pt, 1):17-25. Epub 2004 Dec 24. PMID:16508080 doi:10.1107/S1744309104031501
|
