2q3n
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(New page: 200px<br /><applet load="2q3n" size="450" color="white" frame="true" align="right" spinBox="true" caption="2q3n, resolution 3.50Å" /> '''Agglutinin from Abru...)
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Revision as of 11:38, 21 November 2007
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Agglutinin from Abrus Precatorius (APA-I)
Overview
Abrin and agglutinin-I from the seeds of Abrus precatorius are type II, ribosome-inactivating proteins that inhibit protein synthesis in, eukaryotic cells. The two toxins share a high degree of sequence, similarity; however, agglutinin-I is weaker in its activity. We compared, the kinetics of protein synthesis inhibition by abrin and agglutinin-I in, two different cell lines and found that approximately 200-2000-fold higher, concentration of agglutinin-I is needed for the same degree of inhibition., Like abrin, agglutinin-I also induced apoptosis in the cells by triggering, the intrinsic mitochondrial pathway, although at higher concentrations as, compared with abrin. The reason for the decreased toxicity of agglutinin-I, became apparent on the analysis of the crystal structure of agglutinin-I, obtained by us in comparison with that of the reported structure of abrin., The overall protein folding of agglutinin-I is similar to that of abrin-a, with a single disulfide bond holding the toxic A subunit and the, lectin-like B-subunit together, constituting a heterodimer. However, there, are significant differences in the secondary structural elements, mostly, in the A chain. The substitution of Asn-200 in abrin-a with Pro-199 in, agglutinin-I seems to be a major cause for the decreased toxicity of, agglutinin-I. This perhaps is not a consequence of any kink formation by a, proline residue in the helical segment, as reported by others earlier, but, due to fewer interactions that proline can possibly have with the bound, substrate.
About this Structure
2Q3N is a Protein complex structure of sequences from Abrus precatorius with NAG as ligand. This structure superseeds the now removed PDB entry 2AMZ. Active as rRNA N-glycosylase, with EC number 3.2.2.22 Full crystallographic information is available from OCA.
Reference
Structure-function analysis and insights into the reduced toxicity of Abrus precatorius agglutinin I in relation to abrin., Bagaria A, Surendranath K, Ramagopal UA, Ramakumar S, Karande AA, J Biol Chem. 2006 Nov 10;281(45):34465-74. Epub 2006 Jun 13. PMID:16772301
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