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Key reference
DOI no: 10.1111/j.1742-4658.2007.05906.x FEBS J 274:3695-3703 (2007) PubMed id: 17608716 ![]()
Crystal structures of a family 19 chitinase from Brassica juncea show flexibility of binding cleft loops. W.Ubhayasekera, C.M.Tang, S.W.Ho, G.Berglund, T.Bergfors, M.L.Chye, S.L.Mowbray. ![]()
ABSTRACT ![]()
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Brassica juncea chitinase is an endo-acting, pathogenesis-related protein that is classified into glycoside hydrolase family 19, with highest homology (50-60%) in its catalytic domain to class I plant chitinases. Here we report X-ray structures of the chitinase catalytic domain from wild-type (apo, as well as with chloride ions bound) and a Glu234Ala mutant enzyme, solved by molecular replacement and refined at 1.53, 1.8 and 1.7 A resolution, respectively. Confirming our earlier mutagenesis studies, the active-site residues are identified as Glu212 and Glu234. Glu212 is believed to be the catalytic acid in the reaction, whereas Glu234 is thought to have a dual role, both activating a water molecule in its attack on the anomeric carbon, and stabilizing the charged intermediate. The molecules in the various structures differ significantly in the conformation of a number of loops that border the active-site cleft. The differences suggest an opening and closing of the enzyme during the catalytic cycle. Chitin is expected to dock first near Glu212, which will protonate it. Conformational changes then bring Glu234 closer, allowing it to assist in the following steps. These observations provide important insights into catalysis in family 19 chitinases.
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Literature references that cite this PDB file's key reference
PubMed id Reference
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19629717 W.Ubhayasekera, R.Rawat, S.W.Ho, M.Wiweger, S.Von Arnold, M.L.Chye, and S.L.Mowbray (2009).
The first crystal structures of a family 19 class IV chitinase: the enzyme from Norway spruce.Plant Mol Biol, 71, 277-289.
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18669819 Y.Guan, S.Ramalingam, D.Nagegowda, P.W.Taylor, and M.L.Chye (2008).
Brassica juncea chitinase BjCHI1 inhibits growth of fungal phytopathogens and agglutinates Gram-negative bacteria.J Exp Bot, 59, 3475-3484. The most recent references are shown first. Citation data come partly from CiteXplore and partly from an automated harvesting procedure. Note that this is likely to be only a partial list as not all journals are covered by either method. However, we are continually building up the citation data so more and more references will be included with time.