Structural highlights
4mx1 is a 1 chain structure with sequence from Castor bean. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
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| Ligands: | , , |
| Related: | 1rtc, 1ift, 1br6, 3px8, 4hup, 4hv3, 4mx5 |
| Activity: | rRNA N-glycosylase, with EC number 3.2.2.22 |
| Resources: | FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT |
Function
[RICI_RICCO] Ricin is highly toxic to animal cells and to a lesser extent to plant cells. The A chain acts as a glycosidase that removes a specific adenine residue from an exposed loop of the 28S rRNA (A4324 in mammals), leading to rRNA breakage. As this loop is involved in elongation factor binding, modified ribosomes are catalytically inactive and unable to support protein synthesis. The A chain can inactivate a few thousand ribosomes per minute, faster than the cell can make new ones. Therefore a single A chain molecule can kill an animal cell. The B chain binds to beta-D-galactopyranoside moieties on cell surface glycoproteins and glycolipids and facilitates the entry into the cell of the A chain; B chains are also responsible for cell agglutination (Lectin activity).
Publication Abstract from PubMed
Several 7-aminoamido-pterins were synthesized to evaluate the electronic and biochemical subtleties observed in the 'linker space' when N-{N-(pterin-7-yl)carbonylglycyl}-l-phenylalanine 1 was bound to the active site of RTA. The gylcine-phenylalanine dipeptide analogs included both amides and thioamides. Decarboxy gly-phe analog 2 showed a 6.4-fold decrease in potency (IC50 = 128 muM), yet the analogous thioamide 7 recovered the lost activity and performed similarly to the parent inhibitor (IC50 = 29 muM). Thiourea 12 exhibited an IC50 nearly six times lower than the oxo analog 13. All inhibitors showed the pterin head-group firmly bound in their X-ray structures yet the pendants were not fully resolved suggesting that all pendants are not firmly bound in the RTA linker space. Calculated log P values do not correlate to the increase in bioactivity suggesting other factors dominate.
Sulfur incorporation generally improves Ricin inhibition in pterin-appended glycine-phenylalanine dipeptide mimics.,Wiget PA, Manzano LA, Pruet JM, Gao G, Saito R, Monzingo AF, Jasheway KR, Robertus JD, Anslyn EV Bioorg Med Chem Lett. 2013 Dec 15;23(24):6799-804. PMID:24432385[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Wiget PA, Manzano LA, Pruet JM, Gao G, Saito R, Monzingo AF, Jasheway KR, Robertus JD, Anslyn EV. Sulfur incorporation generally improves Ricin inhibition in pterin-appended glycine-phenylalanine dipeptide mimics. Bioorg Med Chem Lett. 2013 Dec 15;23(24):6799-804. PMID:24432385
