5JU9: Structure Of A Beta-1,4-mannanase, Ssgh134, In Complex With Man3

The enzymatic cleavage of beta-1,4-mannans is achieved by endo-beta-1,4-mannanases, enzymes involved in germination of seeds and microbial hemicellulose degradation, and which have increasing industrial and consumer product applications. beta-Mannanases occur in a range of families of the CAZy sequence-based glycoside hydrolase (GH) classification scheme including families 5, 26, and 113. In this work we reveal that beta-mannanases of the newly described GH family 134 differ from other mannanase families in both their mechanism and tertiary structure. A representative GH family 134 endo-beta-1,4-mannanase from a Streptomyces sp. displays a fold closely related to that of hen egg white lysozyme but acts with inversion of stereochemistry. A Michaelis complex with mannopentaose, and a product complex with mannotriose, reveal ligands with pyranose rings distorted in an unusual inverted chair conformation. Ab initio quantum mechanics/molecular mechanics metadynamics quantified the energetically accessible ring conformations and provided evidence in support of a 1C4 --> 3H4double dagger --> 3S1 conformational itinerary along the reaction coordinate. This work, in concert with that on GH family 124 cellulases, reveals how the lysozyme fold can be co-opted to catalyze the hydrolysis of different polysaccharides in a mechanistically distinct manner.
PDB ID: 5JU9Download
MMDB ID: 144981
PDB Deposition Date: 2016/5/10
Updated in MMDB: 2016/11
Experimental Method:
x-ray diffraction
Resolution: 1.18  Å
Source Organism:
Similar Structures:
Biological Unit for 5JU9: monomeric; determined by author and by software (PISA)
Molecular Components in 5JU9
Label Count Molecule
Protein (1 molecule)
Molecule annotation
Chemicals (5 molecules)
* Click molecule labels to explore molecular sequence information.

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