4mck

Publication Abstract from PubMed

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 DeltaN), which lacks the hevein-like domain. ChitA DeltaN and a mutant form (ChitA DeltaN-EQ) were expressed and purified; enzyme assays showed that ChitA DeltaN activity was comparable to the full-length enzyme. Mutation of Glu62 to Gln (ChitA DeltaN-EQ) abolished chitinase activity without disrupting substrate binding, demonstrating that Glu62 is directly involved in catalysis. A crystal structure of ChitA DeltaN-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.

Crystallographic structure of ChitA, a glycoside hydrolase family 19, plant class IV chitinase from Zea mays.,Chaudet MM, Naumann TA, Price NP, Rose DR Protein Sci. 2014 Feb 6. doi: 10.1002/pro.2437. PMID:24616181^[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.