1LL4 image
Deposition Date 2002-04-26
Release Date 2002-09-25
Last Version Date 2023-08-16
Entry Detail
PDB ID:
1LL4
Keywords:
Title:
STRUCTURE OF C. IMMITIS CHITINASE 1 COMPLEXED WITH ALLOSAMIDIN
Biological Source:
Source Organism:
Host Organism:
Method Details:
Experimental Method:
Resolution:
2.80 Å
R-Value Free:
0.25
R-Value Work:
0.19
Space Group:
P 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:CHITINASE 1
Chain IDs:A, B, C, D
Chain Length:392
Number of Molecules:4
Biological Source:Coccidioides immitis
Ligand Molecules
Primary Citation
THE STRUCTURE OF AN ALLOSAMIDIN COMPLEX WITH THE Coccidioides IMMITIS CHITINASE DEFINES A ROLE FOR A SECOND ACID RESIDUE IN SUBSTRATE-ASSISTED MECHANISM
J.Mol.Biol. 320 293 302 (2002)
PMID: 12079386 DOI: 10.1016/S0022-2836(02)00444-8

Abstact

Allosamidin is a known inhibitor of class 18 chitinases. We show that allosamidin is a competitive inhibitor of the fungal chitinase CiX1 from Coccidioides immitis, with a K(i) of 60 nM. We report the X-ray structure of the complex and show that upon inhibitor binding the side-chain of Asp169 rotates to form an ion pair with the oxazolinium cation. The mechanism of action is thought to involve protonation of the leaving group by Glu171 and substrate assistance by the sugar acetamido moiety to form an oxazoline-like intermediate. We converted both amino acid residues to the corresponding amide and found that each mutation effectively abolishes enzyme activity. X-ray structures show the mutant enzymes retain the basic wild-type structure and that the loss of mutant activity is due to their altered chemical properties. The high affinity of allosamidin, and its similarity to the putative reaction intermediate, suggests it is a transition state analog. This helps validate our contention that the role of Asp169 is to electrostatically stabilize the reaction transition state.

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