This old version of Proteopedia is provided for student assignments while the new version is undergoing repairs. Content and edits done in this old version of Proteopedia after March 1, 2026 will eventually be lost when it is retired in about June of 2026.
Apply for new accounts at the new Proteopedia. Your logins will work in both the old and new versions.
1chk
From Proteopedia
STREPTOMYCES N174 CHITOSANASE PH5.5 298K
Overview
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.
About this Structure
1CHK is a Single protein structure of sequence from Streptomyces sp.. Full crystallographic information is available from OCA.
Reference
X-ray structure of an anti-fungal chitosanase from streptomyces N174., Marcotte EM, Monzingo AF, Ernst SR, Brzezinski R, Robertus JD, Nat Struct Biol. 1996 Feb;3(2):155-62. PMID:8564542 Page seeded by OCA on Fri May 2 12:44:18 2008
