2aai

Crystallographic refinement of ricin to 2.5 Angstroms

spinqualitylabelsall models 2aai, resolution 2.50Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2aai is a 2 chain structure with sequence from Castor bean. The September 2005 RCSB PDB Molecule of the Month feature on Cholera Toxin by David S. Goodsell is 10.2210/rcsb_pdb/mom_2005_9. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: BGC, BMA, GAL, MAN, NAG, NDG Activity: rRNA N-glycosylase, with EC number 3.2.2.22 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum 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). 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 plant cytotoxin ricin consists of two disulfide-linked chains, each of about 30,000 daltons. An initial model based on a 2.8 A MIR electron density map has been refined against 2.5 A data using rounds of hand rebuilding coupled with either a restrained least squares algorithm or molecular dynamics (XPLOR). The last model (9) has an R factor of 21.6% and RMS deviations from standard bond lengths and angles of 0.021 A and 4.67 degrees, respectively. Refinement required several peptide segments in the original model to be adjusted translationally along the electron density. A wide range of lesser changes were also made. The RMS deviation of backbone atoms between the original and model 9 was 1.89 A. Molecular dynamics proved to be a very powerful refinement tool. However, tests showed that it could not replace human intervention in making adjustments such as local translations of the peptide chain. The R factor is not a completely satisfactory indicator of refinement progress; difference Fouriers, when observed carefully, may be a better monitor. Crystallographic refinement of ricin to 2.5 A.,Rutenber E, Katzin BJ, Ernst S, Collins EJ, Mlsna D, Ready MP, Robertus JD Proteins. 1991;10(3):240-50. PMID:1881880 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Ricin

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