1LL4

STRUCTURE OF C. IMMITIS CHITINASE 1 COMPLEXED WITH ALLOSAMIDIN

Summary for 1LL4

• Entry DOI: 10.2210/pdb1ll4/pdb
• Related: 1D2K 1LL6 1LL7
• Descriptor: CHITINASE 1, 2-acetamido-2-deoxy-beta-D-allopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-allopyranose, ALLOSAMIZOLINE, ... (4 entities in total)
• Functional Keywords: beta-alpha barrel, enzyme-inhibitor complex, hydrolase
• Biological source: Coccidioides immitis
• Total number of polymer chains: 4
• Total formula weight: 177421.79

Authors

Bortone, K.,Monzingo, A.F.,Ernst, S.,Robertus, J.D. (deposition date: 2002-04-26, release date: 2002-09-25, Last modification date: 2023-08-16)

Primary citation

BORTONE, K.,MONZINGO, A.F.,ERNST, S.,ROBERTUS, J.D.
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

PubMed Abstract: 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.

PubMed: 12079386
DOI: 10.1016/S0022-2836(02)00444-8

Experimental method

X-RAY DIFFRACTION (2.8 Å)