2q3n
From Proteopedia
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==Overview== | ==Overview== | ||
| - | Abrin and agglutinin-I from the seeds of Abrus precatorius are type II | + | 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== | ==About this Structure== | ||
| - | 2Q3N is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Abrus_precatorius Abrus precatorius] with <scene name='pdbligand=NAG:'>NAG</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. This structure | + | 2Q3N is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Abrus_precatorius Abrus precatorius] with <scene name='pdbligand=NAG:'>NAG</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. This structure supersedes the now removed PDB entry 2AMZ. Active as [http://en.wikipedia.org/wiki/rRNA_N-glycosylase rRNA N-glycosylase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.2.22 3.2.2.22] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2Q3N OCA]. |
==Reference== | ==Reference== | ||
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[[Category: rRNA N-glycosylase]] | [[Category: rRNA N-glycosylase]] | ||
[[Category: Bagaria, A.]] | [[Category: Bagaria, A.]] | ||
| - | [[Category: Karande, A | + | [[Category: Karande, A A.]] |
| - | [[Category: Ramagopal, U | + | [[Category: Ramagopal, U A.]] |
[[Category: Ramakumar, S.]] | [[Category: Ramakumar, S.]] | ||
[[Category: Surendranath, K.]] | [[Category: Surendranath, K.]] | ||
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[[Category: ribosome-inactivating protein]] | [[Category: ribosome-inactivating protein]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 18:35:34 2008'' |
Revision as of 16:35, 21 February 2008
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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 as ligand. This structure supersedes 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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