X-ray structure of an anti-fungal chitosanase from streptomyces N174.Marcotte, E.M., Monzingo, A.F., Ernst, S.R., Brzezinski, R., Robertus, J.D.
(1996) Nat Struct Biol 3: 155-162
- PubMed: 8564542
- DOI: https://doi.org/10.1038/nsb0296-155
- Primary Citation of Related Structures:
- PubMed Abstract:
We report the 2.4 A X-ray crystal structure of a protein with chitosan endo-hydrolase activity isolated from Streptomyces N174. The structure was solved using phases acquired by SIRAS from a two-site methyl mercury derivative combined with solvent flattening and non-crystallographic two-fold symmetry averaging, and refined to an R-factor of 18.5%. The mostly alpha-helical fold reveals a structural core shared with several classes of lysozyme and barley endochitinase, in spite of a lack of shared sequence. Based on this structural similarity we postulate a putative active site, mechanism of action and mode of substrate recognition. It appears that Glu 22 acts as an acid and Asp 40 serves as a general base to activate a water molecule for an SN2 attack on the glycosidic bond. A series of amino-acid side chains and backbone carbonyl groups may bind the polycationic chitosan substrate in a deep electronegative binding cleft.
Department of Chemistry and Biochemistry, University of Texas, Austin 78712, USA.