1LTG
THE ARG7LYS MUTANT OF HEAT-LABILE ENTEROTOXIN EXHIBITS GREAT FLEXIBILITY OF ACTIVE SITE LOOP 47-56 OF THE A SUBUNIT
Summary for 1LTG
| Entry DOI | 10.2210/pdb1ltg/pdb |
| Descriptor | HEAT-LABILE ENTEROTOXIN, ... (4 entities in total) |
| Functional Keywords | enterotoxin |
| Biological source | Escherichia coli More |
| Total number of polymer chains | 7 |
| Total formula weight | 86879.29 |
| Authors | Van Den Akker, F.,Hol, W.G.J. (deposition date: 1995-06-13, release date: 1995-09-15, Last modification date: 2024-10-30) |
| Primary citation | van den Akker, F.,Merritt, E.A.,Pizza, M.,Domenighini, M.,Rappuoli, R.,Hol, W.G. The Arg7Lys mutant of heat-labile enterotoxin exhibits great flexibility of active site loop 47-56 of the A subunit. Biochemistry, 34:10996-11004, 1995 Cited by PubMed Abstract: 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 We report here the crystal structure of an inactive single-site mutant of LT in which arginine 7 of the A subunit has been replaced by a lysine residue.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) PubMed: 7669757DOI: 10.1021/bi00035a005 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (2.4 Å) |
Structure validation
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