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Biochemical and Structural Characterization of the Carbohydrate Transport Substrate-binding-protein SP0092
Published on: October 2, 2017
The first identification of carbohydrate binding modules specific to chitosan
Shoko Shinya1, Takayuki Ohnuma1, Reina Yamashiro1
1From the Department of Advanced Bioscience, Kinki University, Nara 631-8505 Japan.
The Journal of Biological Chemistry
|August 30, 2013
Summary
The study shows that two carbohydrate-binding modules (DD1 and DD2) from a chitosanase exhibit synergistic binding to chitosan oligosaccharides, with DD1 showing higher affinity. This interaction facilitates chitosan hydrolysis.
Area of Science:
- Biochemistry
- Carbohydrate Chemistry
- Enzymology
Background:
- Chitosanase enzymes play a crucial role in degrading chitosan, a polysaccharide derived from chitin.
- Carbohydrate-binding modules (CBMs) are essential for substrate recognition and binding in glycoside hydrolases.
- The Paenibacillus sp. IK-5 chitosanase possesses two CBMs (DD1 and DD2) at its C-terminus, belonging to the CBM32 family.
Purpose of the Study:
- To characterize the binding abilities of individual and combined CBMs (DD1, DD2, and DD1+DD2) from Paenibacillus sp. IK-5 chitosanase.
- To investigate the binding affinity and specificity of these CBMs towards chitosan oligosaccharides of varying lengths.
- To elucidate the molecular interactions between the CBMs and chitosan oligosaccharides.
Main Methods:
- Production and purification of three recombinant proteins: DD1, DD2, and tandem DD1+DD2.
- Thermal unfolding experiments to assess protein stability in the presence of different oligosaccharides.
- Isothermal titration calorimetry (ITC) to quantify binding affinities and thermodynamic parameters.
- Nuclear Magnetic Resonance (NMR) titration experiments to identify interaction sites.
Main Results:
- Both DD1 and DD2 modules bind to chitosan oligosaccharides, with DD1 exhibiting significantly higher affinity and thermal stabilization effect.
- A synergistic binding effect was observed for the tandem DD1+DD2 construct, indicating enhanced interaction with chitosan.
- ITC and NMR data revealed that the CBMs interact with chitosan oligosaccharides through specific loops, with similar binding sites in both DD1 and DD2.
- The binding affinity was not strongly dependent on oligosaccharide chain length for DD1, but DD2 showed lower affinities.
Conclusions:
- The tandem DD1+DD2 construct demonstrates specificity towards chitosan.
- Individual CBMs synergistically interact with at least two glucosamine units, collectively facilitating efficient chitosan hydrolysis.
- Understanding these CBM-chitosan interactions provides insights into the mechanism of chitosan degradation.
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