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Crystal structure of Family GH19, Class IV chitinase from Zea maysCrystal structure of Family GH19, Class IV chitinase from Zea mays
Structural highlights
FunctionCHIA_MAIZE Defense against chitin-containing fungal pathogens (PubMed:1551872, Ref.6). Hydrolyzes glycol chitin and tetra-N-acetylchitotetraose in vitro (PubMed:28328103). Its action is countered by fungal polyglycine hydrolases and fungalysin, that cleave the chitin-binding domain from the protein (PubMed:21453431, PubMed:24627966, PubMed:25966977, PubMed:35240278, PubMed:36762862, Ref.6).[1] [2] [3] [4] [5] [6] [7] [8] Publication Abstract from PubMedMaize 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[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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