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| [[Image:2z48.gif|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_2z48| PDB=2z48 | SCENE= }} | | {{STRUCTURE_2z48| PDB=2z48 | SCENE= }} |
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| '''Crystal Structure of Hemolytic Lectin CEL-III Complexed with GalNac'''
| | ===Crystal Structure of Hemolytic Lectin CEL-III Complexed with GalNac=== |
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| ==Overview==
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| CEL-III is a Ca(2+)-dependent hemolytic lectin, isolated from the marine invertebrate Cucumaria echinata. The three-dimensional structure of CEL-III/GalNAc and CEL-III/methyl alpha-galactoside complexes was solved by x-ray crystallographic analysis. In these complexes, five carbohydrate molecules were found to be bound to two carbohydrate-binding domains (domains 1 and 2) located in the N-terminal 2/3 portion of the polypeptide and that contained beta-trefoil folds similar to ricin B-chain. The 3-OH and 4-OH of bound carbohydrate molecules were coordinated with Ca(2+) located at the subdomains 1alpha, 1gamma, 2alpha, 2beta, and 2gamma, simultaneously forming hydrogen bond networks with nearby amino acid side chains, which is similar to carbohydrate binding in C-type lectins. The binding of carbohydrates was further stabilized by aromatic amino acid residues, such as tyrosine and tryptophan, through a stacking interaction with the hydrophobic face of carbohydrates. The importance of amino acid residues in the carbohydrate-binding sites was confirmed by the mutational analyses. The orientation of bound GalNAc and methyl alpha-galactoside was similar to the galactose moiety of lactose bound to the carbohydrate-binding site of the ricin B-chain, although the ricin B-chain does not require Ca(2+) ions for carbohydrate binding. The binding of the carbohydrates induced local structural changes in carbohydrate-binding sites in subdomains 2alpha and 2beta. Binding of GalNAc also induced a slight change in the main chain structure of domain 3, which could be related to the conformational change upon binding of specific carbohydrates to induce oligomerization of the protein.
| | The line below this paragraph, {{ABSTRACT_PUBMED_17977832}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 17977832 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_17977832}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Pore-forming]] | | [[Category: Pore-forming]] |
| [[Category: Toxin]] | | [[Category: Toxin]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 19:56:04 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 08:48:20 2008'' |
