The family 36 carbohydrate-binding module of Paenibacillus xylaniclasticus TW1 xylanase: Characterization and recognition in epidermal tissue of sweet potato roots

Abstract

Paenibacillus xylaniclasticus TW1 was able to aerobically produce a multienzyme complex. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the crude enzyme preparation revealed at least 12 proteins that were bound to insoluble cellulose. Only the band representing cellulose-bound protein 12 (CBP12) from SDS-PAGE was identified as xylanase family 11 with a carbohydrate-binding module family 36 (CBM36) using matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry (MALDI-TOF/TOF MS). In this report, CBM36 of P. xylaniclasticus TW1 (PxTW1CBM36) was cloned, expressed, purified and studied for binding characteristic. The results found that PxTW1CBM36 displayed broad binding ability to polysaccharides which high affinity for xylan and insoluble cellulose. Interestingly, this is the first report indicated that CBM36 had an affinity for insoluble cellulose. Although the amino acid residues involved in PxTW1CBM36 binding were conserved, the binding capacity of PxTW1CBM36 do not perturb by the addition of ethylenediaminetetraacetic acid (EDTA). It is possible that PxTW1CBM36 had different binding mechanisms with other CBM36. In addition, the binding characteristic of CBM36 on polysaccharides embedded within plant cell walls was also elucidated. It displayed the strong recognition for ligands located in epidermal tissue of sweet potato roots. Therefore, this study might provide a new tool for targeting enzymes to surface of plant.