Download MendeleyCrystallographic structure of ChitA, a glycoside hydrolase family 19, plant class IV chitinase from Zea mays.
Chaudet, M.M., Naumann, T.A., Price, N.P., Rose, D.R.(2014) Protein Sci 23: 586-593
- PubMed: 24616181
- DOI: https://doi.org/10.1002/pro.2437
- Primary Citation of Related Structures:
4MCK - PubMed Abstract:
Maize ChitA chitinase is composed of a small, hevein-like domain attached to a carboxy-terminal chitinase domain. During fungal ear rot, the hevein-like domain is cleaved by secreted fungal proteases to produce truncated forms of ChitA. Here, we report a structural and biochemical characterization of truncated ChitA (ChitA ΔN), which lacks the hevein-like domain. ChitA ΔN and a mutant form (ChitA ΔN-EQ) were expressed and purified; enzyme assays showed that ChitA ΔN activity was comparable to the full-length enzyme. Mutation of Glu62 to Gln (ChitA ΔN-EQ) abolished chitinase activity without disrupting substrate binding, demonstrating that Glu62 is directly involved in catalysis. A crystal structure of ChitA ΔN-EQ provided strong support for key roles for Glu62, Arg177, and Glu165 in hydrolysis, and for Ser103 and Tyr106 in substrate binding. These findings demonstrate that the hevein-like domain is not needed for enzyme activity. Moreover, comparison of the crystal structure of this plant class IV chitinase with structures from larger class I and II enzymes suggest that class IV chitinases have evolved to accommodate shorter substrates.
Organizational Affiliation:
Department of Biology, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1.
