Structure of jack bean chitinase.
The structure of jack bean chitinase was solved at 1.8 A resolution by molecular replacement. It is an alpha-helical protein with three disulfide bridges. The active site is related in structure to animal and viral lysozymes. However, unlike in lysozyme, the architecture of the active site suggests a single-step cleavage. According to this mechanism, Glu68 is the proton donor and Glu90 assists in the reaction by moving towards the substrate and recruiting a water molecule that acts as the nucleophile. In this model, a water molecule was found in contact with Glu90 O(epsilon1) and Thr119 O(gamma) at a distance of 3.0 and 2.8 A, respectively. The model is in accordance with the observed inversion mechanism.
Hahn
M
M
Institut für Biochemie, Charité, Humboldt-Universität, Monbijoustrasse 2, 10117 Berlin, Germany. michael.hahn@charite.de
Hennig
M
M
Schlesier
B
B
Höhne
W
W
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002645:Chickens; D002688:Chitinases / Q000737:chemistry* / Q000302:isolation & purification; D018360:Crystallography, X-Ray; D004527:Egg Proteins / Q000737:chemistry; D007887:Fabaceae / Q000201:enzymology*; D001467:Hordeum / Q000201:enzymology; D006860:Hydrogen Bonding; D008969:Molecular Sequence Data; D009113:Muramidase / Q000737:chemistry; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification; D010946:Plants, Medicinal; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012639:Seeds / Q000201:enzymology; D017386:Sequence Homology, Amino Acid; D014867:Water / Q000737:chemistry
D004527:Egg Proteins; D010940:Plant Proteins; D014867:Water; D002688:Chitinases; D009113:Muramidase