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| [[Image:1cnv.gif|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_1cnv| PDB=1cnv | SCENE= }} | | {{STRUCTURE_1cnv| PDB=1cnv | SCENE= }} |
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| '''CRYSTAL STRUCTURE OF CONCANAVALIN B AT 1.65 A RESOLUTION'''
| | ===CRYSTAL STRUCTURE OF CONCANAVALIN B AT 1.65 A RESOLUTION=== |
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| ==Overview==
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| Seeds of Canavalia ensiformis (jack bean) contain besides large amounts of canavalin and concanavalin A, a protein with a molecular mass of 33,800 which has been named concanavalin B. Although concanavalin B shares about 40% sequence identity with plant chitinases belonging to glycosyl hydrolase family 18, no chitinase activity could be detected for this protein. To resolve this incongruity concanavalin B was crystallised and its three-dimensional structure determined at 1.65 A (1 A = 0.1 nm) resolution. The structure consists of a single domain with a (beta/alpha)8 topology. A 30 amino acid residue long loop occurs between the second beta-strand of the barrel and the second alpha-helix. This extended loop is unusual for the (beta/alpha)8 topology, but appears in a similar conformation in the structures of the seed protein narbonin and several chitinases as well. Two non-proline cis-peptide bonds are present in the structure of concanavalin B: Ser34-Phe, and Trp265-Asn. This structural feature is rarely observed in proteins, but could also be identified in the three-dimensional structures of family 18 chitinases and narbonin in coincident positions. In the chitinases the aromatic residues of the non-proline cis-peptides have been proposed to have a function in the binding of the substrate. The region in concanavalin B, where in chitinases the active site is located, shows two significant differences. First, the catalytic glutamic acid is a glutamine in concanavalin B. Second, although part of the substrate binding cleft of the chitinases is present in concanavalin B, it is much shorter. From this we conclude that concanavalin B and family 18 chitinases are closely related, but that concanavalin B has lost its enzymatic function. It still may act as a carbohydrate binding protein, however.
| | The line below this paragraph, {{ABSTRACT_PUBMED_7490746}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 7490746 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_7490746}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Chitin binding protein]] | | [[Category: Chitin binding protein]] |
| [[Category: Plant chitinase]] | | [[Category: Plant chitinase]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 12:55:54 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 21:00:01 2008'' |
