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| | {{STRUCTURE_1tii| PDB=1tii | SCENE= }} | | {{STRUCTURE_1tii| PDB=1tii | SCENE= }} |
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| - | '''ESCHERICHIA COLI HEAT LABILE ENTEROTOXIN TYPE IIB'''
| + | ===ESCHERICHIA COLI HEAT LABILE ENTEROTOXIN TYPE IIB=== |
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| - | ==Overview==
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| - | BACKGROUND: Cholera toxin from Vibrio cholerae and the type I heat-labile enterotoxins (LT-Is) from Escherichia coli are oligomeric proteins with AB5 structures. The type II heat-labile enterotoxins (LT-IIs) from E. coli are structurally similar to, but antigenically distinct from, the type I enterotoxins. The A subunits of type I and type II enterotoxins are homologous and activate adenylate cyclase by ADP-ribosylation of a G protein subunit, G8 alpha. However, the B subunits of type I and type II enterotoxins differ dramatically in amino acid sequence and ganglioside-binding specificity. The structure of LT-IIb was determined both as a prototype for other LT-IIs and to provide additional insights into structure/function relationships among members of the heat-labile enterotoxin family and the superfamily of ADP-ribosylating protein toxins. RESULTS: The 2.25 A crystal structure of the LT-IIb holotoxin has been determined. The structure reveals striking similarities with LT-I in both the catalytic A subunit and the ganglioside-binding B subunits. The latter form a pentamer which has a central pore with a diameter of 10-18 A. Despite their similarities, the relative orientation between the A polypeptide and the B pentamer differs by 24 degrees in LT-I and LT-IIb. A common hydrophobic ring was observed at the A-B5 interface which may be important in the cholera toxin family for assembly of the AB5 heterohexamer. A cluster of arginine residues at the surface of the A subunit of LT-I and cholera toxin, possibly involved in assembly, is also present in LT-IIb. The ganglioside receptor binding sites are localized, as suggested by mutagenesis, and are in a position roughly similar to the sites where LT-I binds its receptor. CONCLUSIONS: The structure of LT-IIb provides insight into the sequence diversity and structural similarity of the AB5 toxin family. New knowledge has been gained regarding the assembly of AB5 toxins and their active-site architecture.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_8805549}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 8805549 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_8805549}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Enterotoxin]] | | [[Category: Enterotoxin]] |
| | [[Category: Ganglioside receptor]] | | [[Category: Ganglioside receptor]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 09:59:17 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 04:55:48 2008'' |
Revision as of 01:55, 29 July 2008
Template:STRUCTURE 1tii
ESCHERICHIA COLI HEAT LABILE ENTEROTOXIN TYPE IIB
Template:ABSTRACT PUBMED 8805549
About this Structure
1TII is a Protein complex structure of sequences from Escherichia coli. Full crystallographic information is available from OCA.
Reference
Crystal structure of a new heat-labile enterotoxin, LT-IIb., van den Akker F, Sarfaty S, Twiddy EM, Connell TD, Holmes RK, Hol WG, Structure. 1996 Jun 15;4(6):665-78. PMID:8805549
Page seeded by OCA on Tue Jul 29 04:55:48 2008
