1tii
From Proteopedia
(New page: 200px<br /><applet load="1tii" size="450" color="white" frame="true" align="right" spinBox="true" caption="1tii, resolution 2.25Å" /> '''ESCHERICHIA COLI HEA...) |
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| - | [[Image:1tii.jpg|left|200px]]<br /><applet load="1tii" size=" | + | [[Image:1tii.jpg|left|200px]]<br /><applet load="1tii" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1tii, resolution 2.25Å" /> | caption="1tii, resolution 2.25Å" /> | ||
'''ESCHERICHIA COLI HEAT LABILE ENTEROTOXIN TYPE IIB'''<br /> | '''ESCHERICHIA COLI HEAT LABILE ENTEROTOXIN TYPE IIB'''<br /> | ||
==Overview== | ==Overview== | ||
| - | BACKGROUND: Cholera toxin from Vibrio cholerae and the type I heat-labile | + | 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. |
==About this Structure== | ==About this Structure== | ||
| - | 1TII is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http:// | + | 1TII is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1TII OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Escherichia coli]] | [[Category: Escherichia coli]] | ||
[[Category: Protein complex]] | [[Category: Protein complex]] | ||
| - | [[Category: Akker, F | + | [[Category: Akker, F Van Den.]] |
| - | [[Category: Hol, W | + | [[Category: Hol, W G.J.]] |
[[Category: adp-ribosyl transferase]] | [[Category: adp-ribosyl transferase]] | ||
[[Category: adp-ribosylation]] | [[Category: adp-ribosylation]] | ||
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[[Category: ganglioside receptor]] | [[Category: ganglioside receptor]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 15:13:50 2008'' |
Revision as of 13:13, 21 February 2008
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ESCHERICHIA COLI HEAT LABILE ENTEROTOXIN TYPE IIB
Overview
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.
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
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