4X0V

Structure of a GH5 family lichenase from Caldicellulosiruptor sp. F32

Summary for 4X0V

• Entry DOI: 10.2210/pdb4x0v/pdb
• Descriptor: Beta-1,3-1,4-glucanase (2 entities in total)
• Functional Keywords: hydrolase, glycosidase, lichenase
• Biological source: Caldicellulosiruptor sp. F32
• Total number of polymer chains: 8
• Total formula weight: 367064.31

Authors

Meng, D.,Liu, X.,Wang, X.,Li, F.,Feng, Y. (deposition date: 2014-11-24, release date: 2015-11-25, Last modification date: 2023-11-08)

Primary citation

Meng, D.D.,Liu, X.,Dong, S.,Wang, Y.F.,Ma, X.Q.,Zhou, H.,Wang, X.,Yao, L.S.,Feng, Y.,Li, F.L.
Structural Insights into the Substrate Specificity of a Glycoside Hydrolase Family 5 Lichenase from Caldicellulosiruptor sp. F32
Biochem. J., 2017

PubMed Abstract: Glycoside hydrolase (GH) family 5 is one of the largest GH families with various GH activities including lichenase, but the structural basis of the GH5 lichenase activity is still unknown. A novel thermostable lichenase F32EG5 belonging to GH5 was identified from an extremely thermophilic bacterium sp. F32. F32EG5 is a bi-functional cellulose and a lichenan-degrading enzyme, and exhibited a high activity on β-1,3-1,4-glucan but side activity on cellulose. Thin-layer chromatography and NMR analyses indicated that F32EG5 cleaved the β-1,4 linkage or the β-1,3 linkage while a 4--substitued glucose residue linked to a glucose residue through a β-1,3 linkage, which is completely different from extensively studied GH16 lichenase that catalyses strict endo-hydrolysis of the β-1,4-glycosidic linkage adjacent to a 3--substitued glucose residue in the mixed-linked β-glucans. The crystal structure of F32EG5 was determined to 2.8 Å resolution, and the crystal structure of the complex of F32EG5 E193Q mutant and cellotetraose was determined to 1.7 Å resolution, which revealed that the exit subsites of substrate-binding sites contribute to both thermostability and substrate specificity of F32EG5. The sugar chain showed a sharp bend in the complex structure, suggesting that a substrate cleft fitting to the bent sugar chains in lichenan is a common feature of GH5 lichenases. The mechanism of thermostability and substrate selectivity of F32EG5 was further demonstrated by molecular dynamics simulation and site-directed mutagenesis. These results provide biochemical and structural insights into thermostability and substrate selectivity of GH5 lichenases, which have potential in industrial processes.

PubMed: 28838949
DOI: 10.1042/BCJ20170328

Experimental method

X-RAY DIFFRACTION (2.798 Å)