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1ct1

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[[Image:1ct1.gif|left|200px]]
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{{STRUCTURE_1ct1| PDB=1ct1 | SCENE= }}
{{STRUCTURE_1ct1| PDB=1ct1 | SCENE= }}
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'''CHOLERA TOXIN B-PENTAMER MUTANT G33R BOUND TO RECEPTOR PENTASACCHARIDE'''
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===CHOLERA TOXIN B-PENTAMER MUTANT G33R BOUND TO RECEPTOR PENTASACCHARIDE===
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==Overview==
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The wide range of receptor binding affinities reported to result from mutations at residue Gly 33 of the cholera toxin B-pentamer (CTB) has been most puzzling. For instance, introduction of an aspartate at this position abolishes receptor binding, whereas substitution by arginine retains receptor affinity despite the larger side chain. We now report the structure determination and 2.3-A refinement of the CTB mutant Gly 33--&gt;Arg complexed with the GM1 oligosaccharide, as well as the 2.2-A refinement of a Gly 33--&gt;Asp mutant of the closely related Escherichia coli heat-labile enterotoxin B-pentamer (LTB). Two of the five receptor binding sites in the Gly 33--&gt;Arg CTB mutant are occupied by bound GM1 oligosaccharide; two other sites are involved in a reciprocal toxin:toxin interaction; one site is unoccupied. We further report a higher resolution (2.0 A) determination and refinement of the wild-type CTB:GM1 oligosaccharide complex in which all five oligosaccharides are seen to be bound in essentially identical conformations. Saccharide conformation and binding interactions are very similar in both the CTB wild-type and Gly 33--&gt;Arg mutant complexes. The protein conformation observed for the binding-deficient Gly 33--&gt;Asp mutant of LTB does not differ substantially from that seen in the toxin:saccharide complexes. The critical nature of the side chain of residue 33 is apparently due to a limited range of subtle rearrangements available to both the toxin and the saccharide to accommodate receptor binding. The intermolecular interactions seen in the CTB (Gly 33--&gt;Arg) complex with oligosaccharide suggest that the affinity of this mutant for the receptor is close to the self-affinity corresponding to the toxin:toxin binding interaction that has now been observed in crystal structures of three CTB mutants.
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(as it appears on PubMed at http://www.pubmed.gov), where 9232653 is the PubMed ID number.
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{{ABSTRACT_PUBMED_9232653}}
==About this Structure==
==About this Structure==
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[[Category: Oligosaccharide]]
[[Category: Oligosaccharide]]
[[Category: Toxin/receptor complex]]
[[Category: Toxin/receptor complex]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 13:05:03 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 21:19:21 2008''

Revision as of 18:19, 30 June 2008

Image:1ct1.png

Template:STRUCTURE 1ct1

CHOLERA TOXIN B-PENTAMER MUTANT G33R BOUND TO RECEPTOR PENTASACCHARIDE

Template:ABSTRACT PUBMED 9232653

About this Structure

1CT1 is a Single protein structure of sequence from Vibrio cholerae. Full crystallographic information is available from OCA.

Reference

Structural studies of receptor binding by cholera toxin mutants., Merritt EA, Sarfaty S, Jobling MG, Chang T, Holmes RK, Hirst TR, Hol WG, Protein Sci. 1997 Jul;6(7):1516-28. PMID:9232653

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