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The X-ray structure of a chitinase from the pathogenic fungus Coccidioides immitis

Published online by Cambridge University Press:  01 March 2000

THOMAS HOLLIS
Affiliation:
Institute of Cellular and Molecular Biology, Department of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712
ARTHUR F. MONZINGO
Affiliation:
Institute of Cellular and Molecular Biology, Department of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712
KARA BORTONE
Affiliation:
Institute of Cellular and Molecular Biology, Department of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712
STEPHEN ERNST
Affiliation:
Institute of Cellular and Molecular Biology, Department of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712
REBECCA COX
Affiliation:
Department of Clinical Investigation, Texas Center for Infectious Disease, San Antonio, Texas 78223
JON D. ROBERTUS
Affiliation:
Institute of Cellular and Molecular Biology, Department of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712
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Abstract

The X-ray structure of chitinase from the fungal pathogen Coccidioides immitis has been solved to 2.2 Å resolution. Like other members of the class 18 hydrolase family, this 427 residue protein is an eight-stranded β/α-barrel. Although lacking an N-terminal chitin anchoring domain, the enzyme closely resembles the chitinase from Serratia marcescens. Among the conserved features are three cis peptide bonds, all involving conserved active site residues. The active site is formed from conserved residues such as tryptophans 47, 131, 315, 378, tyrosines 239 and 293, and arginines 52 and 295. Glu171 is the catalytic acid in the hydrolytic mechanism; it was mutated to a Gln, and activity was abolished. Allosamidin is a substrate analog that strongly inhibits the class 18 enzymes. Its binding to the chitinase hevamine has been observed, and we used conserved structural features of the two enzymes to predict the inhibitors binding to the fungal enzyme.

Type
Research Article
Copyright
© 2000 The Protein Society

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