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1ltg

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{{STRUCTURE_1ltg| PDB=1ltg | SCENE= }}
{{STRUCTURE_1ltg| PDB=1ltg | SCENE= }}
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'''THE ARG7LYS MUTANT OF HEAT-LABILE ENTEROTOXIN EXHIBITS GREAT FLEXIBILITY OF ACTIVE SITE LOOP 47-56 OF THE A SUBUNIT'''
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===THE ARG7LYS MUTANT OF HEAT-LABILE ENTEROTOXIN EXHIBITS GREAT FLEXIBILITY OF ACTIVE SITE LOOP 47-56 OF THE A SUBUNIT===
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==Overview==
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The heat-labile enterotoxin from Escherichia coli (LT) is a member of the cholera toxin family. These and other members of the larger class of AB5 bacterial toxins act through catalyzing the ADP-ribosylation of various intracellular targets including Gs alpha. The A subunit is responsible for this covalent modification, while the B pentamer is involved in receptor recognition. We report here the crystal structure of an inactive single-site mutant of LT in which arginine 7 of the A subunit has been replaced by a lysine residue. The final model contains 103 residues for each of the five B subunits, 175 residues for the A1 subunit, and 41 residues for the A2 subunit. In this Arg7Lys structure the active site cleft within the A subunit is wider by approximately 1 A than is seen in the wild-type LT. Furthermore, a loop near the active site consisting of residues 47-56 is disordered in the Arg7Lys structure, even though the new lysine residue at position 7 assumes a position which virtually coincides with that of Arg7 in the wild-type structure. The displacement of residues 47-56 as seen in the mutant structure is proposed to be necessary for allowing NAD access to the active site of the wild-type LT. On the basis of the differences observed between the wild-type and Arg7Lys structures, we propose a model for a coordinated sequence of conformational changes required for full activation of LT upon reduction of disulfide bridge 187-199 and cleavage of the peptide loop between the two cysteines in the A subunit.(ABSTRACT TRUNCATED AT 250 WORDS)
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{{ABSTRACT_PUBMED_7669757}}
==About this Structure==
==About this Structure==
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[[Category: Hol, W G.J.]]
[[Category: Hol, W G.J.]]
[[Category: Enterotoxin]]
[[Category: Enterotoxin]]
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Revision as of 19:10, 2 July 2008

Image:1ltg.png

Template:STRUCTURE 1ltg

THE ARG7LYS MUTANT OF HEAT-LABILE ENTEROTOXIN EXHIBITS GREAT FLEXIBILITY OF ACTIVE SITE LOOP 47-56 OF THE A SUBUNIT

Template:ABSTRACT PUBMED 7669757

About this Structure

1LTG is a Protein complex structure of sequences from Escherichia coli. Full crystallographic information is available from OCA.

Reference

The Arg7Lys mutant of heat-labile enterotoxin exhibits great flexibility of active site loop 47-56 of the A subunit., van den Akker F, Merritt EA, Pizza M, Domenighini M, Rappuoli R, Hol WG, Biochemistry. 1995 Sep 5;34(35):10996-1004. PMID:7669757

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