Isothermal titration calorimetric studies on the binding of a family 6 carbohydrate-binding module of Clostridium thermocellum xynA with xlylooligosaccharides.
The family 6 carbohydrate-binding module (CBM) of Clostridium thermocellum XynA was expressed, and the binding equilibria of the CBM with xylooligosaccharides (degree of polymerization DP = 2-8) were observed by isothermal titration calorimetry (ITC) at pH 8. The association constant, Ka, increased with increasing DP from 5 x 10(3) M(-1) (DP = 2) to approximately 5 x 10(5) M(-1) (DP = 5-8) at 20 degrees C. The Ka values at 60 degrees C were about 1/10 of those at 20 degrees C. The binding was found to be an enthalpy-driven reaction. The DP dependence of the thermodynamic parameters of the binding reaction suggested the size of the ligand-binding site to be 5 xylose units long.
Faculty of Bioresources, Mie University, 1515 Kamihamacho, Tsu 514-8507, Japan. sakka@bio.mie-u.ac.jp
Kazuo
K
Sakka
Mari
M
Nakanishi
Mari
M
Sogabe
Takamitsu
T
Arai
Hiroki
H
Ohara
Akiyoshi
A
Tanaka
Tetsuya
T
Kimura
Kunio
K
Ohmiya
D001665:Binding Sites; D002151:Calorimetry / Q000379:methods; D050260:Carbohydrate Metabolism; D002241:Carbohydrates / Q000737:chemistry*; D003013:Clostridium / Q000201:enzymology* / Q000378:metabolism; D043364:Endo-1,4-beta Xylanases; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009844:Oligosaccharides / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D013816:Thermodynamics; D017186:Titrimetry; D014995:Xylosidases / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism*
D002241:Carbohydrates; D009844:Oligosaccharides; D014995:Xylosidases; D043364:Endo-1,4-beta Xylanases