School of Life Sciences and Biotechnology, Korea University, Seoul 136-713, Korea.
Biotechnol Bioeng. 2013 Feb;110(2):401-7. doi: 10.1002/bit.24719. Epub 2012 Sep 18.
Plant expansin proteins induce plant cell wall extension and have the ability to extend and disrupt cellulose. In addition, these proteins show synergistic activity with cellulases during cellulose hydrolysis. BsEXLX1 originating from Bacillus subtilis is a structural homolog of a β-expansin produced by Zea mays (ZmEXPB1). The Langmuir isotherm for binding of BsEXLX1 to microcrystalline cellulose (i.e., Avicel) revealed that the equilibrium binding constant of BsEXLX1 to Avicel was similar to those of other Type A surface-binding carbohydrate-binding modules (CBMs) to microcrystalline cellulose, and the maximum number of binding sites on Avicel for BsEXLX1 was also comparable to those on microcrystalline cellulose for other Type A CBMs. BsEXLX1 did not bind to cellooligosaccharides, which is consistent with the typical binding behavior of Type A CBMs. The preferential binding pattern of a plant expansin, ZmEXPB1, to xylan, compared to cellulose was not exhibited by BsEXLX1. In addition, the binding capacities of cellulose and xylan for BsEXLX1 were much lower than those for CtCBD3.
植物扩展蛋白诱导植物细胞壁扩展，并具有扩展和破坏纤维素的能力。此外，这些蛋白在纤维素水解过程中与纤维素酶表现出协同活性。来源于枯草芽孢杆菌的 BsEXLX1 是玉米（ZmEXPB1）产生的 β-扩展蛋白的结构同源物。BsEXLX1 与微晶纤维素（即 Avicel）结合的 Langmuir 等温线表明，BsEXLX1 与 Avicel 的平衡结合常数与其他 A 型表面结合碳水化合物结合模块（CBM）与微晶纤维素的结合常数相似，BsEXLX1 在 Avicel 上的最大结合位点数也与其他 A 型 CBM 在微晶纤维素上的结合位点数相当。BsEXLX1 不结合纤维寡糖，这与 A 型 CBM 的典型结合行为一致。与 BsEXLX1 相比，植物扩展蛋白 ZmEXPB1 对木聚糖的优先结合模式而不是纤维素。此外，纤维素和木聚糖与 BsEXLX1 的结合能力远低于 CtCBD3。
